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airsmith282
05-13-2009, 10:21 AM
ok well i like htis geeny bought it used for 20 bucks and its only a year old.. and works perfect, anyhow it is very quiet as it is and iam using it to power my shop lights and a few other things all same time.so any how, i made this little rig from some hollow aluim and stainless steel caps fornt and back and made the hole at 9/64, now its even quieter and works really slick i should be able to work in the shop at night now and not distrube my neibours you can hardely hear it at all now..
the main reason i got the genny was to lighen the load on my hydro bill i can run for 12 hours on a tank of gas which is not bad for a 2 stroke motor..and iam never out there that long at a time anymore so it should pay for it self pretty fast id think.. I should metion as well that the orgianl hole out of the exaust pip was 12 Mm so its is a substantional reduction ..

http://i26.photobucket.com/albums/c124/airsmith282/1-1.jpg

http://i26.photobucket.com/albums/c124/airsmith282/2-1.jpg

http://i26.photobucket.com/albums/c124/airsmith282/3-1.jpg

http://i26.photobucket.com/albums/c124/airsmith282/4.jpg

Evan
05-13-2009, 10:33 AM
That's a nice little generator. I have one just like it. They are well made. It's not a good idea to restrict the exhaust that much on a 2 stroke, it will cause overheating and can cause the engine to sieze from lack of lubrication because the oil is carried in with the fuel. Not enough fuel means not enough oil.

Barrington
05-13-2009, 12:46 PM
...so it should pay for it self pretty fast id think..
Might be worth your while looking at this again - 12 hours on a tank of gas sounds good until you do the sums. Here in the UK, power from a 'home generator' will cost somwhere from 5 to 15 times as much as power from the grid.

Although I know gas in Canada is much cheaper (about half what we pay I think), I don't know what you pay for 'hydro', but that's a big gap to make up...

Worth checking out before you spend good tool money on wasted gas :D

Cheers

Willy
05-13-2009, 12:55 PM
What Evan said.

I'd also be VERY surprised if you can produce electricity at a lower cost than the 7.5-8 cents a kWh that Ontario Hydro charges.

Look at the over all cost of running and maintaining a generator for a year vs the power that you can produce, and compare that to your cost of 7.5-8 pennys for every 1000 watts of power per hour.

bborr01
05-13-2009, 01:05 PM
Hi Airsmith,
I have to agree with Barringtons post about the price of grid power vs. home generator power. I use a Honda 2000I inverter generator when I winter in Arizona as I don't have grid power. Last winter I did some calculating the cost and I would get about 5-6 Kwh of power out of a gallon of gas. I used a Kill-a-watt meter to measure the power leaving the generator and into my battery bank. Also keep in mind that these inverter generators are much more effecient because they don't run wide open all the time. Here in Michigan we pay around 12.5 cents /Kwh for power including all the taxes and fees. Gas would have to cost around 75 cents a gallon to break even with power company prices. I also have to agree with Evan about restricting the exaust that much. You might want to use a car muffler or something like it to cut the restriction on the exaust. Hope this info helps.

Duffy
05-13-2009, 02:10 PM
No disrespect, but I think you sold yourself a "bill of goods." I drove through North Bay two weeks ago and you were paying nearly $.90/liter for gasoline. Add twostroke oil and it is over $1.00/litre. You must be drinking nearly a litre an hour under load, (or more.) My shop is fairly well lit, with a dozen two-lite fluorescent units. They are magnetic ballasts, so a good rule of thumb is 100 watts/unit. that means I burn 1.2 Kwh for lights. If you are on a rural rate at $0.15/kwh., that is only $0.18/hour. Unless you are a REALLY efficient multi-tasker, you only average one machine at a time. If it is 2.5 kw. then it operates for $0.375/hr, and that totals only $0.55/hour. What am I missing in this equation? Duffy

madman
05-13-2009, 02:39 PM
Well looks like it will fit on a end of a .22 rifle barrel for in town supressed varmint control.

airsmith282
05-13-2009, 06:50 PM
well iam not runnning all the shop tools wiht it it runs 3 regual bulbs and 2 florcent lights aslo runs my small compressoer as needed which is not to often and it runs m geto blaster and charges my drill batterys and runs my cordless phone so it is running eficent enough for al that and saves my hydro bill a bit,, being thats its summer time now no need to run the lights all the time, it also runs my buffer machine as well when needed,, at 1000 watts 800 running watts and the run time per tank iam getting it is auctully saving me hydro money form the house as right now we are getting rapped for our hydro,, my lath and mill run off the house hydro and this genny will run al lmy lights and stuff and still run the mill if need be .. the restrixtion of the exaust is not an issue with the device i made it does not creat more pressire nor does is restrict the air flow the muffler still does the job its supposed to ,, this thing just makes the sucker run a hell of alot quieter,, 2 stroke or 4 stroke wont make a difference in the lubracation the motor is getting.. its get al the same lube as it did before i installed the extention to the muffler ..

yes gas is abotu 90 cents a liter rightnow this thing is 1.1 gallon so not to bad and so far i have been using its for 3 days now and this is day one witht he extension on it and i have oly used up 1/4 tank of fule, right now my 2 stroke oil is free as i gots a few bottles with a weed wacker i picked up and even to pay for it its still going to be cheaper on my house bill over all and its good on the fule as well.. we wil see after a month or 2 what my total cost a month is going to be for fule and oil but so far after 3 days id say she is doing rather well ..

Evan
05-13-2009, 07:37 PM
the restrixtion of the exaust is not an issue with the device i made it does not creat more pressire nor does is restrict the air flow the muffler still does the job its supposed to ,, this thing just makes the sucker run a hell of alot quieter,, 2 stroke or 4 stroke wont make a difference in the lubracation the motor is getting.. its get al the same lube as it did before i installed the extention to the muffler ..


Restricting the exhaust restricts the amount of fuel it is able to pull in since it DOES increase the back pressure. Try breathing through a soda straw which is about the same size.

Restricting the amount of fuel restricts the amount of oil and WILL cause damage even if it doesn't sieze the engine.

It makes a big difference if it is a 2 stroke cycle as opposed to a 4 stroke cycle since a 4 stroke has an independent supply of oil that is pumped and splashed on the moving parts. The only way a two stroke engine of that type gets any oil is via the fuel.

It would be a shame to ruin your genset because of something so simple to change. It's a nice little generator and worth much more than $20 if it is running well. They sell new for around $150.

Barrington
05-13-2009, 07:59 PM
Only trying to save you cash - have just looked up the specs on your gen:

continuous output 800W (0.8kW)
tank 1.1 US gals = 4.2 litre
running time 7 hours at 50% output (i.e. 0.4kW)

(If you're getting 12 hours per tank that must mean you're using about 200W+)

So a tankful (4.2 litres) produces 7 x 0.5 x 0.8 = 2.8 kWh

So each kWh of electricity generated uses 4.2/2.8 = 1.5 litres of gas @ $0.90 = $1.35 (+ oil)

Each kWh from the Hydro costs how many cents ? :eek:

So at 200W you probably spending an extra $0.20 or more per hour over and above the cost of hydro...

Cheers

airsmith282
05-13-2009, 09:03 PM
well elt me put it to you this way my hydro bill with same items running all the time is costingme an extrra 100. to 150. a month on my bill ,, take that out of the equation and use the genny for same items and not having ot use them al the time cost me how much about 15.00 bucks a to 20 bucks a month, plus oils thats about 40 bucks a month so yup iam saving money using the genny the way iam ..

let also keep in mind here specs mean absoulte BS .. this thing ran all the said items plus i fired up my polisher that sucks more amps then this this saiys it prduces thats with all other items running same time to by the way,, so , id say this thing is well under rated and out performs it self, one guy even ran a 1500 watt heater wiht no problems on the thing so thats pretty decent id say and proves its under rated for what the specs say..

J Tiers
05-13-2009, 11:59 PM
Still have to agree the cost of running that should well exceed the cost of just using the electric...... if not, then you are probably not charging all teh costs against it that are really there, or have over-estimated the cost via normal electric.

Also, 2 stroke engines are usually short-life engines.... not intended for long hour usage. Some are good for as little as 600 hours. or less.

And for sure, that little exhaust hole is likely not gonna work out long term.... Evan's point is good.

Willy
05-14-2009, 12:17 AM
Well all I can say is congratulations!
You've got yourself one helluva little generator.
Not only can it produce power cheaper than the utility companies, but you've also made fools of an awful lot of mechanical and electrical engineers.
My only regret is that I don't have a dozen or so of those little gems humming away in a little shed out back. As you say the little suckers are quiet enough, what with the 9/64's exhaust and all. Maybe that is why they are so fuel efficient...you can't burn much if it can't get out, and all the while putting out twice the rated wattage.

radkins
05-14-2009, 08:23 AM
If that tiny little hole is all there is for the exhaust to escape then there definitly IS a lot of restriction, a LOT of restriction! Two stroke engines are very finicky about the exhaust design and restricting it will have adverse effects even if they are not apparent right now, and yes it will affect lubrication (among other things) for the reasons already stated. That exhaust set-up may seem like a good idea right now due to the noise reduction but in a short time it will get even quieter, in fact it is going to get VERY quiet indeed! :D

Also there is no way, no POSSIBLE way, that thing can produce power cheaper than the grid and you are kidding yourself if you think so!

japcas
05-14-2009, 09:53 AM
let also keep in mind here specs mean absoulte BS .. this thing ran all the said items plus i fired up my polisher that sucks more amps then this this saiys it prduces thats with all other items running same time to by the way,, so , id say this thing is well under rated and out performs it self, one guy even ran a 1500 watt heater wiht no problems on the thing so thats pretty decent id say and proves its under rated for what the specs say..

One thing I'd check next time you run the polisher on the genny. Check the Hz and voltage on the line coming from the genny. When you overload these gas powered genny's, they continue to make power but they slow the engine down while doing it, which slows the line frequency down and voltage as well. Running your polisher at a line frequency a lot lower than 60 can also diminish the life of your polisher motor.

Willy
05-14-2009, 10:06 AM
let also keep in mind here specs mean absoulte BS .. this thing ran all the said items plus i fired up my polisher that sucks more amps then this this saiys it prduces thats with all other items running same time to by the way,, so , id say this thing is well under rated and out performs it self, one guy even ran a 1500 watt heater wiht no problems on the thing so thats pretty decent id say and proves its under rated for what the specs say..



No, all it proves is that you have a non effective generator circuit protection system.
Either it has no circuit breaker or fuse, or it has been replaced with one having a higher rating.

Between the 9/64's exhaust outlet and the electrical circuit protection issues, I don't predict a long life for little Genny.

keelan
05-15-2009, 03:26 AM
airsmith282,

Hang on a second while I put on my hippy hat...

Okay, I'm ready. You have at your disposal one of the cleanest sources of power (hydro), courtesy of your utility company. You choose to instead use a dirty, inefficient two stroke tied to a most likely poorly designed little generator, which is probably converting the potential energy contained in the gasoline to electricity at (I'm being generous here) 30% efficiency. It's unnecessarily wasteful of resources.

I'll put my hippy hat away now. Do I smell patchouli?

I work in a large data center with almost a megawatt of generator capacity. I've seen the electrical bills (hydroelectric), and I've seen the fuel bills (marked diesel, lower price than you see at the pump). I've done the math. I can tell you that I would NOT want to run the facility 24/7 on generator power. It would get prohibitively expensive very quickly.

Once the novelty wears off, you will realize that this is a bad idea.

Evan
05-15-2009, 05:06 AM
. . .most likely poorly designed little generator,. . .


That particular point is not a given. As I said I have one just like it and it is a really nice little unit. Fit and finish are excellent as is the quality of the main casting. It has a variety of nice features including fuel shutoff, 12 VDC charging with separate circuit breaker and included jumper cord and even has a built in fuel screen in the tank filler opening which includes a nested oil measuring cup that stows under the cap. It is a robust design and weighs about 35 lbs. It probably is underrated and likely will run at more than 800 watts output for extended periods, but only if it has sufficient lubrication.

Of course it is impossible to compete with the utility provided power no matter what method you use.

Seastar
05-15-2009, 07:50 AM
To sum it up ---
1. The "muffler" will damage the generator. Take it off and throw it away!
2. It costs much more to produce power with the generator than the grid charges. Save the generator for emergencies.
Bill

Evan
05-15-2009, 07:58 AM
It isn't a very loud unit either although if the original muffler is rusted out it would be a different story.

airsmith282
05-15-2009, 09:05 AM
1 the origianl muffler is still on the genny
2 it has a 12 mm out put hole, which now exits to a 1 inch tube sever inchs long approx 6 inchs which then exits to 3.5 MM or 9/64 the amount of presser commingout the 12 mm hole form the auctual muffle produces very little presser now expand that in a 6 inch by 1 in hole and then allow it to exit the 9/64 hole aka 3.5 mm there is no harmful back pressure being created if any at all.3 there is alreay about 600 hours or more on this genny when i got it..so mcuh for the life span of a 2 stroke
4iam running 16:1 mix,,right now as it had runing issues on the 50:1 next mix will be 40:1

5 lack of lube its a 2 stroke the lube is in the gas its not lubed after the exaust leaves the motor ..even a 4 stroke is lubed from the under side,, anyhow what ever..

6 as mention the items iam running in it are no where near hitting its 800 running watts out of 1000w its rated for..

7 when i put hte polisher on and had all that other stuff hooke at same time the genney slowed right down for a second or 2 the speed back up you would too if some one tried to aks for more amps then you had left to give..

8 iam not ruuning the genny 24/7 its only runing a few hours a day and only as needed..

9 the power comming in my house in town here is not as clean as you mght thinnk we prived that to the hydro company sever times over and they dont know what to say about it ,,

10. if i blow it up i lose 20.00 bucks , but i think ill be the one thats right in the end and this sucker will give me years of use ..


11 to the guy that checed the specs they look the same but are not
mine has the 2.2 HP engine and is rated at 1000 with 850 runnig watts sorry its not in front of me to remeber exactly. anyhow
theone they sell now is 800W running and 950W peak power and has only got 2hp motor ,, in only a year they lowered the specs ,,looks the same but its not ..

12 all the breakers are stock and all work as they should..

13 saving money on my hydo bill this thing can and will do
A iam not using it 24/7
B its less draw due to the fact i get all my amps back for my other tools to run more efficent on the grid aka mill and lath etc..
c for the stuff that is runing on the genny its more then clean enough power to run them.. lets see light bulbs a geto blaster stereo, my phone my charger for my drill, a dremel. and my 3 gallon compressor which draws as it needs to umm oh ya my dremel when i need it.the polisher was something i tried cause i needed to polish a part for my sons bike and it was less hassel to plug it into the genny line thats in the shop and i also thought i wounder it this sucker can handle it man was i impresed , my grinder only draws 2 amp so its well with in specs of the genny as well.. dam i love my toys



ill update you guys if it ever blows up then ill admit your right and iam wronge but only if it blows up due to my many faults that have been listed at me

ok whet to chekc the machine 1000watts 850 running and 2.0 hp motor not 2.2 either way looks like they chaged a few things.,

Evan
05-15-2009, 09:25 AM
Try this some time.

Take a very short piece of garden hose and try to breath through it. It should be no problem, not that much restriction with a 1/2" tube a few inches long. Then try to breathe through one that is a meter long.

Hey, what going on? It's really hard to breath but the hole is the same size, just longer.


Even if your stated measurements are accurate adding any additional restriction after the stock muffler increases the back pressure. Two stroke engines are very sensitive to having the right amount of fuel and lubrication. The lube comes in with the fuel. Back pressure reduces the amount of fuel that the engine can pull in because it reduces the amount of exhaust that leaves every cycle. This means less oil and more friction so more heat and wear.


Yes, using your generator will save money on your hydro bill. It will save about 8 cents every hour you use it.

airsmith282
05-15-2009, 09:50 AM
the big thing here seems to be restriction what about the screen they use on the end of the muffler i done use it anymore and if oyu compile allthe no holes in the screen and put that into the equasion then really my 9/64 hole in my extention is about the same amont as the screen if not its slightly larger but only my a fraction of a MM so really iam not causing any restricon at all and add to the that the out put exacuse travels form the mufflels 12 MM hole down a chamber thats 1 in and then has the 9/64 and also woops or got to mention i had to drill a bottle drain hole of 1/8 at the front of my extension at the bottom , so in all iam not giving any restriction at all or causeing any added back pressure..so it efficent and it does the job it was built for..

anyhow either way i paiy alot more hten 8 cent per hour on my hydro bill for hte house so the genny will save me house costs either way and do the job i bought it for

what pisses me off to no end is i put up a post here to show of a cool gizomo i invented for my genny and i get a **** storm of BS and crap thronw at me and most are saying its going to do this or do that and bla bla bla , man i dont dumpo on your stuff ,and if some of you guys think you know so dam much then PROVE ME TO BE WRONGE I DARE YOU ..

i think out side the box and i use logic and non logic and iam not afraid to try something if it works cool if not well i guess i was wronge no big deal. but dont tell me iam wronge unless you can back it up 100% that your right and iam wronge..

every one said you cant go to the moon well guess what happen
ok now we got space stations and stalites and spy cams in space and all kinds of crap out there and techknoledgey is advancing and so on all the time things people say you can do that its not going to work your going to blow it up .

rotate
05-15-2009, 10:00 AM
...
every one said you cant go to the moon well guess what happen
....

For the record, only people who were uneducated in science and technology thought that.

You should be grateful that the members on this board, many of whom are experts are giving you good advice. Don't expect the board members to offer accolade if you're doing something that's not correct. Just because it works doesn't make it right.

topct
05-15-2009, 10:12 AM
It has been proven that restricting the exhaust on a two stroke engine can widen the torque curve. Exhaust restriction systems are used on a lot of modern motorcycle 2 stroke engines. Although they are variable on the bikes the basic principle would work on a stationary or constant speed engine.

It would be interesting to see how much power increase was gained by restricting the exhaust slightly. The stock system being a comprimise.

As far as the lubrication of the engine. It is always going to get whatever is mixed with the gas. If it is getting less oil it is getting less gas. That equals less power and or rpms.

Willy
05-15-2009, 11:22 AM
First of all airsmith I'm sorry if you've taken offense to our criticisms of your generator mods. I don't believe that any of the members of this forum are here to dump on you, or anybody else for that matter. But when one choses to show a project, it is open to both praise and constructive criticism. Not only in execution and workmanship, but also in how practical the project is. We don't want to see you ruin your genny, or think that you're saving money when you are not. Just helpful advice from one friend to another, nothing else.

When I have everyone tell me that what I'm doing is not practical, I have a decision to make. Either I think to myself...maybe they might know more than I...or everybody's wrong to hell with em, I'll just keep pissin in the wind. Hey, you know what, I'll bet every person here has been on both sides of the fence.

There's an awful lot of experience and knowledge on this board and I'm here to take advantage of it because I sure as hell don't know it all. Sometimes it's hard to admit to oneself that a preconceived notion that one has held for a long time is wrong, but it's better to learn than carry on blindly in the dark.

As far as the generator goes, I'm sorry but it goes against everything that man has learned about internal combustion engine design and the generation of electricity since the 1800's. I could write volumes about industrial generation systems that I've worked with, some very efficient designs in both the electronics and power plants. But the one thing they all had in common was that they existed only either as backup in mission critical applications, or they were there because it was not practical to have grid power at a particular location.

When one looks at the cost of these systems, maintenance, efficiency, and eventual replacement, they are indeed very inefficient compared to grid power. All this in spite of the best and most efficient engine designs and generator technology.

So don't feel bad if you haven't found the goose that lays the golden egg.

Evan
05-15-2009, 01:34 PM
--------------------------------------------------------------------------------

It has been proven that restricting the exhaust on a two stroke engine can widen the torque curve. Exhaust restriction systems are used on a lot of modern motorcycle 2 stroke engines. Although they are variable on the bikes the basic principle would work on a stationary or constant speed engine.


I would think that the manufacturer has already optimized the design. Also, what good does it do to widen the torque curve on an engine that always runs at near the same rpm? As I have said, it is a well made unit with a lot of attention to the details. For a good example of a small 2 stroke engine overheating due to exhaust restriction just put a muffler on a model airplane engine. The power drops drastically and the head temperature goes way up.

Evan
05-15-2009, 01:38 PM
PROVE ME TO BE WRONGE I DARE YOU

If I have time today or tommorrow I will fire up my genset like yours and measure the head temperature with and without a slight exhaust restriction. I have a nice infrared thermometer that is good to over 500 degrees that has proven to be very accurate so it won't be difficult to do. I am interested to see the result.

topct
05-15-2009, 03:09 PM
I would think that the manufacturer has already optimized the design. Also, what good does it do to widen the torque curve on an engine that always runs at near the same rpm? As I have said, it is a well made unit with a lot of attention to the details. For a good example of a small 2 stroke engine overheating due to exhaust restriction just put a muffler on a model airplane engine. The power drops drastically and the head temperature goes way up.

I would be surprised if whoever build the unit did anything other than gather existing pieces, bolt them together and put their name sticker on it. In fact I'll bet you could get that same generator with your name on it.

The design has been optimized only in the final cost of the thing.

As far as model airplane engines go. The fitting of a proper exhaust pipe will increase it's output. Yes it will cause a rise in head temps, but not enough to be a problem.

Evan
05-15-2009, 03:58 PM
There are several brands on the market of this genset that are sold around the world. I tracked down the actual manufacturer and it is a company in China that is one of the very few that has been in business for long time making IC engine powered equipment. I don't recall the name as that was a couple of years ago but I wanted to know who made it because the quality is surprisingly good.

As far as optimizing for cost, far from it. They could save a bundle of money if they did that. It is much heavier than it needs to be for what most people will use it for and most of that is in the main aluminum casting. Designing a genset isn't a trivial job and you can't just go buy individual pieces to make one. This unit has the engine and alternator integrated as a single unit all in the same casting. Whomever designed it knew what they were doing.

sandman2234
05-15-2009, 04:38 PM
Most of the advice given seems in touch with what I have learned over the span of the last 53 years. A lot of BTDT, and it appears the final answer is simple.
Don't confuse me with the facts, my mind is made up...

Depending on the inlet size of that muffler, it actually could get you in serious trouble here in the U.S.A, but since your not here, enjoy it.
David from jax

radkins
05-15-2009, 07:09 PM
It has been proven that restricting the exhaust on a two stroke engine can widen the torque curve. Exhaust restriction systems are used on a lot of modern motorcycle 2 stroke engines.

Well not exactly, not just simply restricting the exhaust as has been done to that generator. A PROPERLY ENGINEERED restrictive exhaust that consists of an expansion chamber and a restriction from a tube of proper length instead of just a small hole. The idea with the restriction in this case is not to produce backpressure like that "muffler" is doing but to increase exhaust velocity to produce the desired torque curve. Simply reducing the exhaust as has been done here will result in backpressure, reduced lower-end power and higher engine temperatures.


airsmith, with all due respect I fail to see your reasoning about how that small hole will not restrict the exhaust, I re-read your description several times. No matter what size the pipe or how long it is that tiny hole is going to restrict the exhaust in the end, there is just no way around it.

airsmith282
05-15-2009, 08:39 PM
Well not exactly, not just simply restricting the exhaust as has been done to that generator. A PROPERLY ENGINEERED restrictive exhaust that consists of an expansion chamber and a restriction from a tube of proper length instead of just a small hole. The idea with the restriction in this case is not to produce backpressure like that "muffler" is doing but to increase exhaust velocity to produce the desired torque curve. Simply reducing the exhaust as has been done here will result in backpressure, reduced lower-end power and higher engine temperatures.


airsmith, with all due respect I fail to see your reasoning about how that small hole will not restrict the exhaust, I re-read your description several times. No matter what size the pipe or how long it is that tiny hole is going to restrict the exhaust in the end, there is just no way around it.


with all due respect , the screen that was on the muffler reduces just as mcuh if not more so then then the modification i have done, my goal was ro further reduce the sound and it does that rater well ,, also theres no scren on the muffler anymore so its no longer restricting the exaust its now free to open up to the tube area and out the end of the 9/64 hole and the other 1.8 hole which combined with the tube length and inner diameter will still produce more more restriction then what the screen did on the muffer when it was there and the muffer is still on the machine as well so what i have done no one has be able to prove in anyway shape or form that i have done any thing that will cause harm to the genny ,,

where is there proof its hamming anything at all , if i had a tester to test the out put pressue if bet i would be dame close if not bang on to the orgianl set up there for creatingno extra back pressure.. by feel on the hand test both set ups seem to be the same , with no screen , now witht he screen on the muffer only then testing the device i made wiht no screen it seems there is less pressure comming out not alot less but it is noticable so in all iam auctually alling for a tiny bit less back presser which is not goingto in any way harm the genny for the little of the difference there is between the 2 set ups .. and i still get a mcuh quieter running engine so as not to piss off my neibours shoud i wish to work out in the shop late at night...

ok talk to hydro company today there present rate for use is 6 cents per klw hour now thats not bad , except iam paying aobutr 3 times that due to the 3rd party contract we got that we cancelled today sothings should returnback to normal soon and ill see some cheaper bills for a change..

any how iam going to continue doing some tests i fienlly ran out of the 16:1 mix i was running in it now its gota 50:1 in it that is suppoesd to be in there so we shall see how long this tank of gas last and how the genny performs as well.. at the 16:1 it started easy and ran great .. my stpe sone said he had some isseus wth a noise inthe motor when he used it well the 16:1 seems to have cleared that right up so if the thing makes the noise under the 50 to 1 again then we shall try 40:1 and so on , and i just got 5 gallons of gas for free today so it will be cost free experiment for me and i still got lots of my free 2cycle oil left as well..

anyhow my gas powered grinder shludbe ready tomorow or the next day just made the pully for the motor an hour ago , and tonighti am chillaxing so back to the shop tomoorw..

Evan
05-15-2009, 10:01 PM
I ran a test just a short while ago. I restricted the exhaust by about the same amount although since I didn't fasten the restrictor to the muffler it had some leakage as well as passing through the small hole. The hole in the end of your muffler is about only 1/3 the size of the hole in the original muffler. In order to compare you must calculate the area of the hole, not the diameters.

I ran my genset with a 500 watt load in the form of a halogen floodlamp. I let it warm up for half an hour with the restrictor in place. With the restrictor my machine runs about 20 to 30 degrees hotter on the head area by the spark plug. That isn't too bad but I discovered something else surprising. The exhaust gas temperature goes way up which I measured by measuring the muffler temperature.

I took the restricted temperatures first and then took the unrestricted temps so it had to cool down to get to the unrestricted temps. That provides a fairer assesment than the other way around since it could still be warming up. As soon as I removed the restrictor the muffler temp fell by 50 degrees F in less than a minute. That is actually a better indication of the cylinder temperature than the outside temperature of the head. Exhaust gas temp (EGT) is how temperatures are measured on many critical IC engine applications such as aircraft and other air cooled engines.

That amount of temperature increase isn't likely to cause the engine to sieze. It is likely to cause increased varnishing from the higher combustion temperature as indicated by the EGT. Also, the temperature I measured here was on a cool afternoon. Take the same reading on a hot and humid day and you can increase the temperature by more than just the temperature difference. The rate of cooling goes down by the approximate inverse square of the increase in ambient temperature. On a hot day the temperature will be high enough to pose a real problem.

I will post a couple of pictures a bit later after I have supper.

airsmith282
05-16-2009, 12:07 AM
and did you make the restrictor to the same specs as mine,, and using hte same materials as well ..aslo to have it fair you must have and air tight seal on the restricto as i do in order to also be fair and have it work efficently at the same time. other wise all that testing you did was false and misleading..

ill give and an E for Effort , also do this test 2 ways one with a 16:1 mix the other wiht 50:1 and see what the differences are as well ,, iam now running on the 50:1 mix ,,


stay tuned this is interesting.. ill give you the specs for my set up tomorrow,

Evan
05-16-2009, 02:53 AM
and did you make the restrictor to the same specs as mine,, and using hte same materials as well ..aslo to have it fair you must have and air tight seal on the restricto as i do in order to also be fair and have it work efficently at the same time. other wise all that testing you did was false and misleading..



Tell you what, you send me your restrictor for testing and then we will have no possibility for you to find a way to convince yourself that there isn't a problem.

Restriction is restriction for the purpose of measuring the temperature. The exhaust has to leave the engine. It wasn't my purpose to duplicate your device but to show what happens when the outlet for the exhaust is restricted. That is easy to see. Sealing the outlet does not make it more efficient, only quieter.

Sorry I didn't post these images sooner but I fell alsleep after supper.

As you can see I have the same unit.

http://ixian.ca/pics6/gen.jpg

The top number on the readout is the current temp and the bottom is the highest it read.

http://ixian.ca/pics6/gen1.jpg

http://ixian.ca/pics6/gen2.jpg

http://ixian.ca/pics6/gen3.jpg

airsmith282
05-16-2009, 10:23 AM
Tell you what, you send me your restrictor for testing and then we will have no possibility for you to find a way to convince yourself that there isn't a problem.

Restriction is restriction for the purpose of measuring the temperature. The exhaust has to leave the engine. It wasn't my purpose to duplicate your device but to show what happens when the outlet for the exhaust is restricted. That is easy to see. Sealing the outlet does not make it more efficient, only quieter.

Sorry I didn't post these images sooner but I fell alsleep after supper.

As you can see I have the same unit.

http://ixian.ca/pics6/gen.jpg


The top number on the readout is the current temp and the bottom is the highest it read.

http://ixian.ca/pics6/gen1.jpg

http://ixian.ca/pics6/gen2.jpg

http://ixian.ca/pics6/gen3.jpg


Nice pics, anyone can prove that if you restric the out put of the muffler like yu have that its oging to cause a problem, but if you want to priove the my device does infact cause restriction and or problems as many other have also noted that it does then what you all need to do is put your money where your mouth is this means all that have said iam in the wornge here and build my device and run your testes and then if you can prove me to be wornge then ill accept that and will remove the device,, but if you can not prove it then you all owe me an appoligy ..

i dont have to send you nothing its upto you if you want to prove what i did was wronge and this its restricing more air then the original setup then you have to build the device your self ,, ill have a full list of speces this afternoon or by this evening ..

J Tiers
05-16-2009, 10:37 AM
run your testes

???????????????????????

Come on now, don't be a #all-buster about it !

:D

Evan
05-16-2009, 10:54 AM
When your generator dies then send it to me and I will show you why. You have all the information you need already plus some. If you aren't willing to accept help then your only option is to learn from Experience. She is sometimes the most expensive but also the most convincing teacher.

bborr01
05-16-2009, 12:30 PM
Airsmith,
If you want to burn out the gen that is your business.
But you can guess all day long as to the amount of elec. you generate and not come close. See if you can borrow or buy a Kill-a-watt meter. They cost around $30 US. This meter will tell you how much wattage you are actually drawing and a cumulative reading for how many Kwh you have consumed. Then it becomes a simple math problem to figure out what your costs are vs. the cost of buying from the power company. One word of advice on the meter though. When the gen. runs out of gas the meter goes blank so you have to monitor the meter when your gas tank is near empty.
Brian

airsmith282
05-16-2009, 05:21 PM
ill agree on 1 thing here if you reduce the end of hte muffle where hte out put hole is then you will certianly cause alot more back presser which is bad for hte motor , but by adding on to the end of the muffle a long tube in this case approx 6 inch long 1 inch ID and 1 and 1/8 OD and then add on a front cap that has a 9/64 hole and under is another hole thats 1/8 the about that it has to travel threw the tube and it expands the air flow and then out the hole you will not harm the engine it does not add any revs nor does it slow it down either .to the motor like it would by restricking at the muffle it self, as show in EVANS set up his set up is wronge and will cause motor damage, there for i did achive a perfect set up and made the geny more quiet like i had intended ..

ok ill agree on another idea that we only know so much about engines sence the 1800's but new things are being found out everyday.some guy invents an H2 o tourch or runs his car on the stuff and every one is like no way its not true it cant happen well bull crap it did does and well happen all the time ..

iam not an expert on water but i seen some really wild stuff over the years , iam not and expert on enignes i just work on them every day..

evan clean your carb and give her a tune up i got 9 hours on 3/4 of a tank of gas today .. at 50:1 mix , i guess running a few tanks of 16:1 help it who knows ..

i used 3 40 watt bulbs,my big dule 4 foot florcent lites my smaller single flocent light my stereo and even made the compressor fire up a few times . now these are all the items i use on the genny.. other then my cordells phone but its in the house right now ..

anyhow specs will be up tonight for my muffler expansion device its dinner break time now...

3rd thing ill agree on is your likey correct that it will cost me more in fule then using the grid if this was a 24 hour a day running set up but its not so if any thing i might save a few bucks or i might now the next few months will tell that tale to be true or not , i extimate at 5.30 a tank a fule that includes the oil in that.. i predeict ill spend about 50 bucks a month on fule and oil and thats being gererouse and likey ill spend less but we will have to see.. the only way to know for sure is to try it and see what happens ..'

in the mean time while we are waitng for the specs on the muffler add on enjoy the pics of the set up i made from a homelite water pump motor that is now going to run my grinder .. a new post wiht a video will be done onces its all together..


http://i26.photobucket.com/albums/c124/airsmith282/DSC03579.jpg

http://i26.photobucket.com/albums/c124/airsmith282/DSC03580.jpg

http://i26.photobucket.com/albums/c124/airsmith282/th_MOV03581.jpg (http://s26.photobucket.com/albums/c124/airsmith282/?action=view&current=MOV03581.flv)

Evan
05-16-2009, 09:58 PM
So you are saying that if the hole is the same size but in a different location then more exhaust will fit through it? How does that work?


You are right that my test isn't an accurate recreation of your setup. You see, I only restricted the exhaust by about 1/3 of the original outlet. Yours restricts it to only about 1/8th the original.

Here is a comparison of how much I restricted it and how much you have.

http://ixian.ca/pics6/gen4.jpg

The reason your rpms don't change is because the generator has an effective governor. The only way it can keep running with such a small exhaust port is for the pressure to climb much higher than before. That is how the exhaust is able to all fit through such a small orfice. That also means the cylinder pressure is much higher which also means hotter.

As a ballpark guess I would expect that your machine is running about 100 degrees higher than it should. That's a lot and could result in damage to the piston. The higher pressures will wear out the con rod bearings much faster and adding more oil won't change either one.

rotate
05-16-2009, 11:09 PM
ok ill agree on another idea that we only know so much about engines sence the 1800's but new things are being found out everyday.some guy invents an H2 o tourch or runs his car on the stuff and every one is like no way its not true it cant happen well bull crap it did does and well happen all the time ..


OK. That explains everything. I think you're on a wrong forum. :p

airsmith282
05-16-2009, 11:19 PM
evan untill you build the same unit i did and do the test you wont under stand how it works ,, so i never got time today to get the specs up see what happens tomorow, i got invoved in my grinder project ,, any how stay tuned,,

J Tiers
05-16-2009, 11:48 PM
Looking at the device again, and looking at Evan's test, I think the test is ALL WRONG.

The muffler airsmith put on is QUITE DIFFERENT to the test Evan did, and Evan's results are in NO WAY representative of what airsmith is getting.

You folks who are predicting instant engine death are all wet. Look at it again.



evan untill you build the same unit i did and do the test you wont under stand how it works ,, so i never got time today to get the specs up see what happens tomorow, i got invoved in my grinder project ,, any how stay tuned,,

it is DEFINITELY possible to 'know" and accurately predict what will happen in the case of your device. Certainly in the case of the cost of fuel........ I would put a fair amount of money on the idea that you are NOT winning on costs.

I am not certain exactly what Evan did, the length of pipe between the block and the hole will have a rather LARGE effect on the way the thing works. it looks like he has a short length of small diameter pipe, quite different to what you did.

Now, I looked at yours, and there is, upon some more thought, a fair chance that all you made is a type of muffler, and that the predictions of engine death are a bit exaggerated.

I have NO idea what the displacement of that unit is, but the small exhaust hole in the block suggests it isn't very big, since it is a 2 stroke, and can be smaller displacement than a similar power 4 stroke. That's important to the operation. The unit sounds like it is around a 1.5 HP or so, probably no more than 2 HP, if that.

if your pipe length is enough that its volume is at least comparable to the displacement, then when added to the volume inside the exhaust passage, you may have enough volume to accept the exhaust without extreme back pressure.

And, the rest of the cycle, all the time that the exhaust is shut off by the piston, is available as "leak-down time" to allow the pipe to drop back to atmospheric pressure, ready to accept another slug of exhaust. So on that basis, the small hole is much less of a bad effect than predicted by various posters.

it would be a far different story if your small hole were right at the block. Then the blockage would do what has been predicted, raising the back pressure to a huge degree, and heating everything up quite hot.

When the thing is considered ONLY as a hole in the exhaust, and the VOLUME of the extended pipe is NOT considered, it looks bad. But when the ENTIRE picture is viewed, it is not nearly so extreme.

if you added MORE pipe, or fattened the pipe up to allow considerably more volume, I would wager that you could get the head temps back down to nearly the temp attained with the stock muffler. And the SAME hole size could be used......with even less bad effect.

I still don't think you can possibly 'win" on fuel cost vs electric, unless you are really being slammed for electric power costs. Your efficiency of motor is so much lower than a steam plant, and for hydro, well the energy cost per kilowatt is almost undefined, hydro is "green, renewable power".

Evan
05-17-2009, 01:20 AM
Jerry,

If it runs at the same rpm, which it does because of the governor, then the swept volume per minute is the same. If the only way out for that gas is through the 3.5mm hole, which it is, then the only possible result is higher pressure regardless of how much of an expansion chamber there is. Since the governor is able to maintain the same rpm according to the OP, and I believe that to be true from my experience, then the higher pressure that inevitably results reduces the amount of air-fuel mix being inhaled. Burning that mix at higher pressure increases the power output to a degree and opening the throttle more reduces pumping losses which also increases power. Both increase temperature. The gains in power are offset by the increase in exhaust temperature which destroys the input side efficiency gain. This is in keeping with the principle of heat engine operation and the Carnot Limit.

There isn't any way to show that the exit hole, which is approximately 1/8 the area of the muffler exit port, can somehow not significantly increase back pressure and temperature when the engine operates at the same load and rpm as without it.

In my simple test not only is the orfice much bigger but there was significant leakage around the fitting and the muffler port. It had very little effect on the noise level and no noticable effect on rpm but even still it made a significant difference to temperature.

Using an expansion chamber after a conventional muffler has no benefit and if the outlet is restricted as it is then it can only be a detriment.

Doc Nickel
05-17-2009, 02:42 AM
evan untill you build the same unit i did and do the test you wont under stand how it works[...]

-Sorry, but it's not Evan that's misunderstanding the concepts at work here.

First off, your muffler/expansion-chamber/silencer IS a restriction, period, end of conversation. All else being equal, a smaller orifice restricts flow over a larger orifice. This is Physics 101 stuff, right up with water is wet and magnets stick to refrigerators.

Now, it's agreed that your engine does in fact still run, and runs well, with your new muffler in place. No one is disputing that.

But here's the kicker: Just because the engine still runs at the same RPM does NOT mean the muffler is NOT a restriction.

What you've done is increase- drastically- the "dwell", for want of a better term, of the exhaust gas. Each pulse of gas can still exit the muffler fast enough to allow the engine to run, but it takes far longer to do so. The analogy is a balloon; poke it with a pin and all the air is released at once- which makes a short, loud noise. But just let the neck open, and it makes a lower noise, but over a longer period of time.

And that's what you're getting; the exhaust can still leave the engine, it just takes longer- and thus also produces a lower amount of noise.

The problem here is that a 2-stroke relies on the speed of the exhaust gas for proper charge timing. In a properly designed 2-stroke, a charge of exhaust should technically not have actually left the exhaust system before the next exhaust cycle starts. A sort of "reflected wave" should arrive back at the cylinder exhaust port right about the same time most of the subsequent charge has evacuated the cylinder.

This "wave" does two things: one, it helps reduce the amount of unburned charge blown into the exhaust (which lowers fuel efficiency and increases emissions/pollution) and two, it helps increase the charge density in the cylinder.

What your muffler has done is thrown that resonance timing out the window. You've reduced the exhaust speed so much that chances are you're not even getting that "reflected wave" at all- or if you are, it's incorrectly timed, which boils down to the same thing.

Now, the engine still runs. No mystery here, as the engine will run without a muffler or exhaust pipe at all, and will continue to run with even a badly designed one, or just a straight pipe.

The point is, it won't run as well.

That's not my "opinion", nor is it Evan's "opinion" nor Jerry's "opinion". It's established fact, established by the past sixty or eighty years of 2-stroke technology and development.

Restricting the exhaust raises the cylinder head and exhaust temperature because you've increased the amount of time the charge "dwells" inside the engine. The longer the hot gas waits around, the more heat gets transferred to the head and cylinder walls. Again, this is established fact- NASCAR racers, among others, use exhaust gas temps to determine how well an individual cylinder is running- one hot cylinder could point to a mechanical problem like a bent pushrod, loose rocker pivot or weak valvespring.

And of all the engine designs out there, in a 2-stroke especially, heat equals death. The crank is both lubricated and cooled by the incoming charge. If that charge is slowed- as it must be if the exhaust is slowed- and the overall temperature is raised by the aformentioned additional heat-soak time, then you're shortening the lifespan of the engine, probably by a significant percentage.

Now, this is not always readily apparent- that longer heat soak time also helps extract a bit more "work" out of the charge, so the apparent engine HP loss is not as great as it might be in a 4-stroke. Plus, you'll actually see a reduction in fuel consumption, since each intake charge is less dense then it otherwise would be.

Those can indeed be "good" things, but they come at the guaranteed expense of a significantly reduced engine life.

Doc.

Sparky_NY
05-17-2009, 08:24 AM
A interesting thread which brings back memories of my days with 2 stroke motorcycles and R/C airplane engines. I remember removing the baffles on my 2 stoke motorcycle expecting more performance and got much less. A 2 stroke (lacking a exhaust valve), needs a certain amount of back pressure to operate efficiently. The generator in question has a exhaust outlet that is tiny by all accounts and could certainly cause all the previously mentioned problems unless more is going on here than meets the eye. What I am considering is that the original muffler coupled with the add-on is now functioning like a expansion chamber type exhaust. Expansion chambers have been around a long time and work well to soup-up a 2 stroker. Jerrys post above describes the function of a expansion chamber pretty well. More power does mean more heat so a rise in temperature would be expected but is that a bad thing if its not excessive? Guys have added expansion chambers for years to 2-stroke motorcycles, chainsaws, R/C engines and more to increrase the power output. This may well be what is happening in this case. Normally a expansion chamber would be a complete exhaust system replacing the original muffler but if the muffler volume is about right a custom "tip" like the one in question might just cause expansion chamber type operation. I am guessing this motor is around 30-50 cc's.

I am not saying this is operating in the mode of the well proven expansion chamber type exhaust, its just food for thought.

Another thing that came to mind in reading this thread was the R/C engines that use a "exhaust throttle". For throttle purposes those engines had a variable restriction in the exhaust outlet and just a smooth bore carb.

As for generating ones own power with a gas generator (any type) cheaper than utility power, well.... many have tried, far more have investigated the possibility but its always been found to not be possible on a small scale. I would expect this to be more true than ever with a 2-stroke which are known for poor fuel economy compared to a 4 cycle along with the added cost of 2-stroke oil.

Still, this is yet another very interesting thread here on the forum.

J Tiers
05-17-2009, 09:36 AM
Jerry,

If it runs at the same rpm, which it does because of the governor, then the swept volume per minute is the same. If the only way out for that gas is through the 3.5mm hole, which it is, then the only possible result is higher pressure regardless of how much of an expansion chamber there is.

Sorry, Evan...... you are correct in detail, bit WRONG in conclusion.

While you are correct that the gas has to leave via the hole, and ANY restriction, even a designed muffler, is a restriction increasing temperatures, your conclusion of "inevitable engine death" as expressed in earlier posts, is WRONG, because of bad assumptions, and a failure to understand or apply how the engine works.

BTW, it is NOT the "swept volume" that is involved, it is the volume occupied by the generated exhaust gases AT ATMOSPHERIC PRESSURE. because that is where they are going....

And a very important point is the TIME available for exhaust to exit...... which you have ignored.


-Sorry, but it's not Evan that's misunderstanding the concepts at work here.

First off, your muffler/expansion-chamber/silencer IS a restriction, period, end of conversation. All else being equal, a smaller orifice restricts flow over a larger orifice. This is Physics 101 stuff, right up with water is wet and magnets stick to refrigerators.
.......................That's not my "opinion", nor is it Evan's "opinion" nor Jerry's "opinion". It's established fact, established by the past sixty or eighty years of 2-stroke technology and development.


"sorry" right back atcha.....

Yes, but NO.

And that would be about 120 years of two stroke development, incidentally....... not 60 or 80.

It isn't my "opinion" either.... it's PHYSICS, which both you and Evan are ignoring when it suits your argument to do so, and invoking when that is best for your point..

Thought experiment:

1) let the exhaust be totally free, NO PIPE....

There is STILL a restriction..... called a valve, and head passage. There is a pressure increase, and a temp rise due to it. is it a fatal one? NO, presumably. You can, for purposes of the experiment, call this the "zero backpressure point". It isn't zero, but it is the least that engine can have.

2) Let the 9/64 (0.140") hole be in a plug screwed into the exhaust port.

There is a severe restriction..... the exhaust cannot exit the cylinder except through the hole. The time available is short, less than one half revolution of the crank, and much of the exhaust stays in the cylinder.

This is the "maximum backpressure point". it isn't truly max, but for the given conditions of rpm and hole size, it is the most you get.

3) let the exhaust pipe exit into a rigid container of 1000 times the swept volume, or better, 1000 times the volume of the exhaust gases at atmospheric. Drill the 0.140" hole somewhere in the container.

The backpressure from that VERY SAME HOLE will be far LESS than from case 2, "Physics 101" handwaving notwithstanding.

Why is this?

because the very large volume will accept the exhaust pulses without much incremental pressure increase for each pulse of exhaust..... i.e. low PEAK backpressure.

AND because that fact allows the large volume to AVERAGE the flow over an entire crankshaft rotation, INSTEAD of requiring all the exhaust to exit in the short time the ports are open.

This is called a "muffler", a device you are possibly familiar with. Any small engine muffler is made this way, although there may be more than one chamber, more than one hole, etc, and the entire thing will be a lot smaller than 1000 times the exhaust volume.

There will STILL be a backpressure, of course, which will take some time to build up in the large volume. But it will STOP rising at some point when the pressure is sufficient to allow the available volume of exhaust to exit the hole precisely during one rotation.

4) now make that volume smaller and smaller..... There will be essentially no increase in average pressure over a large change in the volume.

What WILL happen is that the PEAK pressure will begin to rise, slowly at first, and faster as the external volume begins to approach the exhaust gas volume. Eventually, the peak pressure drags up the average pressure.

By selecting the external volume, you can establish any average backpressure you want, between the "zero point" and the "maximum backpressure". Each will have an associated peak pressure.

The designers of "mufflers" make a compromise of flow restriction, average pressure, and peak pressure, which is supposed to provide the best performance and the least noise at the least cost. Generally, it seems the noise is reduced less, and ill effects of backpressure is minimized.

The "peak" backpressure is the most important, because that directly affects the ability to clear the cylinder of exhaust and bring in a new charge. The AVERAGE backpressure has less effect.

I don't know what the external volume of airsmith's pipe is, nor the cylinder size, etc.

What I DO know, and what YOU can know also, if you open your mind up and think a bit, is that it is perfectly possible to come up with an external volume and hole size which will be capable of handling the exhaust pulses with an acceptable peak backpressure.

That hole size can be SIGNIFICANTLY SMALLER than the exhaust passage in the block.

I don't know the direct effect of that particular 0.140" hole size. I DO know that it is going to have less bad effect than the effect observed in a short pipe experiment such as Evan's, because Evan failed to distinguish between PEAK and AVERAGE backpressure..

Evan
05-17-2009, 10:26 AM
BTW, it is NOT the "swept volume" that is involved, it is the volume occupied by the generated exhaust gases AT ATMOSPHERIC PRESSURE. because that is where they are going....



That makes no sense. They have to get there through a fixed hole in a fixed time from a fixed cylinder volume at a fixed rpm.



And a very important point is the TIME available for exhaust to exit...... which you have ignored.


That is where your mistake lies Jerrry. The time involved hasn't changed. The engine is still running at the same RPM so the time allowed for the exhaust to leave the system is the same but the orifice is much smaller. That translates directly to higher pressure, higher temperature and higher wear.




It isn't my "opinion" either.... it's PHYSICS, which both you and Evan are ignoring when it suits your argument to do so, and invoking when that is best for your point..



Nope. No ignoring going on. At least, not by me OR Doc.


I don't know the direct effect of that particular 0.140" hole size. I DO know that it is going to have less bad effect than the effect observed in a short pipe experiment such as Evan's, because Evan failed to distinguish between PEAK and AVERAGE backpressure..


That might be true if I had installed the restrictor directly on the exhaust port of the engine. Apparently you haven't noticed the size of the muffler that lies BEFORE the restrictor. It is plenty large enough to average the pressure before it gets to leave by the restrictor and there will be no appreciable difference between adding a restriction as I did or as the OP did except the size of the restriction.

[edit]

I can't figure out why you are digging yourself such a deep hole Jerry?

Deja Vu
05-17-2009, 10:44 AM
It's not so simple...as arguements on both sides show.

airsmith282 (http://bbs.homeshopmachinist.net/member.php?u=7898) has achieved his goal of making his generator less noisy at the expense of longevity. Or maybe not.... Did the added expansion chamber allow the engine to approach a more optimum operating temperature that was sacrificed by the manufacturer for the sake of compactness?
I would suspect that if airsmith282 (http://bbs.homeshopmachinist.net/member.php?u=7898) added some fins to his secondary expansion chamber, the cooling effect on the exhaust gases may further reduce the pulsing back pressure.

airsmith282
05-17-2009, 10:47 AM
good morring all wow its been busy here while i was sleeping, anyhow if oyu restrict the exit port on the muffle below specs you will slow down the engine rpms and starr to choke the engine thats a fact and its not happeing , as for rpm speed the more load you put on the genny the faster the engine will run that is a fact , if your engin is not raising in rpm when you increase the load to the genny then you need to fix your genny. now the reduction of the port here does not take affect until 6 inchs or so down the tube the inner cavity of the tube is 1 inch and complety hollow so no restriction what so ever until the exause vents out 2 holes at the from 1 is 9/64 the other under it is 1/8 which also allows any liquied buld up to leak or blow out as well as exhaust..

now if i plug the 1/8 hole it has little effect like none, now if i leave it alone and plug my 9/64 hole it starts to choke the motor out. slow it down and it increases the back pressure then , but combined 1//8 and 9/64 togeter is no affecton back presse rpms are the same with my device as without sound levels it what has changed, so if i was really restricing the air flow any rpms will be affected thats a fact you just cant escape..

now you take a car ok stcok from the factoy there pretty quiet right lots of back presser there and so on cars need a certian amounte so we are told..wel thats BS in most cases,, remove junk form the factory and put on a cherry bomb exhaust what happens here now is its loud its a hollow pipe with a fiber glass pack in there that helps alter the sound a bit but its now wide open and there goes 99% of your back pressure but your motor runs cooler now gas miliage is increased and horsepower goes up 2 HP per cylinder wow what and improvment..

go back to the factoty muffler gas milage takes a dump,motor runs hot as hell again but she is quiet..

a harely most of them i seen run on a straight pipe so no real restriction or back pressure there,, hell take the pipes off and still drive it only a bit louder then,, put a quiet exhaust on the fat boy harely which is normaly loud whats going to happen ,,well its going to be alot quieter but back pressure is goingto build up and and your goingto have some engine problems on the way mabey three is a 30% chance, see every motor is designed differently.. and there for some need back pressure to run right some dont need any at all but stil are ok with some restriction ,., to over restrict any engine is bad for it, to know if you are restrcting the engine to mcuh you will notice

1 rpms will slow down
2 motor will run way to quiet part of rpms slow way down
3 yes the temps wil go above safe limits
4 you will know with in a few hours on most engines if you did damage

a weed wacker engine most have a make belive muffle split it apart ther eis noting in there at all,sometimes not even a spark arrestor screen not all weed wackers need one or use one and some that dont use one and you add it in you will thne have problems maybe mabey not depends on the size and location of the screen and how big the holes are and how you have tuned the carb and so on ..

lawn mowers wow they run pretty looud most of them muffles are very much like weed wackers 4 ot 2 stroke dont matter..
and you can mod them to..

evans experment was a joke , it only proved that he restricted the out put to much and he didnt even get a proper fit on the neck to seal off leaky areas..he also did not make the same deivce or even one similer, so he has done nothing to defend his claim on my device i think thats hte right words anyhow he hasnet poved me wronge just proved he knows how to over restrict the airflow to make things act the way he says it will with out even using the proper set up to prove mine to be wronge..

i dont care much for the laws of phycis and so on , man knows only waht makes sence and tends to stick to it and say this is right and that is wronge so long as man contiunes to stay on this plane of knowledge man will not advance ,, there for i like to go against the grain of what we all know and i dont belive nothing untill what we know now proves me wronge then all thats goingto do is encourge me to find another soloution that i hadnt thought of ,, in fact iam going to build another one but this time no end cap and check the results and then ill double the opening to waht it is now so ill have 3 of these things all built when iam done then iam going to make one with baffles in it like a ca set up and see how that work while not buildingit i can tell you right now keeping al the baffles the same hole size in them as the exit hole of the muffle thats there now will reduce the sound to a throty sound and will indeed cause back presser the motor will not like at all and will raise the temps of the motor to high and will also reduce the rpms by approx 100 rpm best guess on the rpm there so damage will happen at that point ,

ona 4 stroke motor this would be efficent and work well but on a 2 stroke nope not going to be good for it..

any how i gota run for now i must get to my gas grinder and get it running and get thet specs up for those of you that wish to prove my device harmfull

by the way to be fair let see this done in real time put up some vidoes so we now your not BSing us with your findings ,, for thoes that done have a 14MM drill might one to pick one up its a nice tight fit on the end of that geeny there is also a set screw used as well to ensure a tighter fit..

you will also need some 316 or 303 SS ill have all the mesurements today and materials needed for thoes that are going to build this thing you also have to use the same genny as well ,, we all know even has one the same as mine..

dont get me wronge here iam not trying to pick an argument but if you want to prove something to be wornge or not safe to the motor in this case you have to back up what you say and do the same experiment in order to get the findings

to just say nope its not going to work cause all the books say so is the wornge approche not all books are 100% correct..

some one told me once you will not get that valve to work this was in a pellet gun it is what it is and you cant alter it to make it do this or that boy did i prove him and the others wronge, one other guy was like you gota lessing the tension on the hammer spring to get more power , nope sorry you gota add a bit more and mod the port larger and lighten the valve return spring. etc..

ok so iam right they were wronge ,,

angled ports on an air gun valve are not effictive unless everything is made on the same angle other wise your still shooting air at 90 not ont he 45 that you are after what you do below the barrel must also take place in the barrel other wise you have gained NOTHING

here is food for thought
take and airgun that has a 1/16 trasfer port the valve port is say 9/64 auctualy its larger ok now the gun shoots at 415 FPS whats my gain in fps if i only drill the transfer port to 3.5MM this would be on a crosman 1377, if is has a candian valve its going to run at 530 fps at 10 pumps if its an american valve in the gun then its going to be realy close to 600 about 580 to 592 average..

ok the 2289 rifle its only a valve change goto us valve and its running 496 noting else has been altered now dril the trasfer port to 3.5MM 550 to 560 fps now..
now these speeds change alot depend on the barameteric presser in your area i have seen as much at + or - 60 fps dpending onthe area and so on tempture out side as well and so on ,,

had i build my device to be a muffler that used baffles which restrict the air flow alot i would have blowen the motor in a few hours iam sure..if you over muffle a muffler by adding on another muffler then you are asking for problems i more or less opened up the air flow and the shrunk the end a the end the amount of presser by the time it reaches the the end of the tube is next to nothing so there for it can not harm the motor, i have simpley taken a door in a room that was open and the sound anoying and closed the door so i wont hear it as much and the sound gets redirected else where..

if you take a muzzle break that only has an exit hole all your sound moves forward and can be lound if you take the same sound and now add in say 3 top side holes to vent the gas upward now very little sound moves forward and it prevents most of the muzle flip that occures on most airguns cause it forces the barrel down as the gun fires..

if oyu have the hols 3 on each side the air moves to the sides and so does the sound and almost not sound in the front now its all been redirected ,,

it gives the appearence of reduction but its simply moved the sound waves to and area that obsorbes the sound wiht out causeing restriction or very little for that matter..

radkins
05-17-2009, 10:50 AM
if your pipe length is enough that its volume is at least comparable to the displacement, then when added to the volume inside the exhaust passage, you may have enough volume to accept the exhaust without extreme back pressure.


That just does not make much sense past a couple of engine revolutions, That tiny hole will cause a restriction regardless of the pipe. After the first couple of revolutions the pressure will build in the pipe and then you are back to square one, if the exhaust is discharged into any kind of pipe, muffler or whatever and can only eventually exit by that tiny orifice then back pressure will certainly be the end result.


A 2 stroke (lacking a exhaust valve), needs a certain amount of back pressure to operate efficiently.

Again there seems to be confusion as to the purpose of the restriction in a "tuned" exhaust. It is not simply back pressure the engine needs it is a controlled exhaust velocity, that's why those baffles in the motorcycle exhaust were in the end of a small tube (the tube may be inside a muffler but it is there). A small diameter exhaust tube is used to increase the velocity of the exhaust which in turn will affect the scavenging of the cylinder to more completely remove exhaust and help create more of a vacuum to pull more air/fuel charge into the cylinder. If the exhaust velocity is too high then at low RPM it will not only remove the burned gas from the cylinder it will also pull part of the incoming fuel charge out with it. Baffles of a properly chosen size are sometimes used to slow the exhaust velocity (NOT TO CREATE BACK PRESSURE IN THE CYLINDER!) and control timing of the exhaust/fuel charge. These baffles can be varied as to the amount of restriction to control the exhaust velocity and thus change the torque curve of the engine. Simply removing the baffles from the (properly designed) exhaust will have the effect of increasing exhaust velocity and raising the torque curve and increasing power in the upper part of the RPM band but at the expense of torque loss at lower RPM. The problem with removing the baffles from most factory motorcycle exhaust systems, as was described above, is that usually it will move the peak power above the maximum RPM range of the engine and result in an over-all loss of power. What has been done to that generator is to simply restrict the exhaust and create cylinder back pressure which will raise cylinder temperature and shorten engine life, what he has done does not in any way compare to removing or adding baffles to a tuned expansion chamber or factory motorcycle muffler.

A two stroke engine benefits from CONTROLLED EXHAUST VELOCITY not simply back pressure!

Evan
05-17-2009, 10:50 AM
His expansion chamber won't change anything as it comes AFTER the normal exhaust system. Cooling the exhaust gas to reduce volume would make a slight difference but there isn't sufficient time to cool it much. The expansion chamber would need to be many times larger.

BTW, no intent to poke fun at you but I just saw this the other day and found it funny.

Deja Moo: The feeling that you have heard this bull before...

Evan
05-17-2009, 10:53 AM
anyhow if oyu restrict the exit port on the muffle below specs you will slow down the engine rpms and starr to choke the engine thats a fact and its not happeing ,

Of course it isn't happening. The generator has a GOVERNOR.

Deja Vu
05-17-2009, 10:57 AM
His expansion chamber won't change anything as it comes AFTER the normal exhaust system. Cooling the exhaust gas to reduce volume would make a slight difference but there isn't sufficient time to cool it much. The expansion chamber would need to be many times larger.

BTW, no intent to poke fun at you but I just saw this the other day and found it funny.

Deja Moo: The feeling that you have heard this bull before...

No problem, Evan, I'm able to laugh at myself(and others) at any given time without worrying about invoking memories of that famous song "feelings". :D

radkins
05-17-2009, 11:31 AM
The generator has a GOVERNOR.


Exactly, and what is happening is the governor is opening the throttle in an attempt to maintain engine RPM at it's set speed and overcome the exhaust restriction. Because of this restriction the cylinder will not be able to completely scavenge the exhaust gases and the wider throttle opening will result in lower air velocity (Bernoulli's principle) through the carburetor. Lower intake velocity is going to result in lower vacuum on the metering jets which in turn means a leaner mixture. The leaner mixture means a hotter combustion temperature and the lower velocity also means less ram effect into the crankcase as the piston reaches TDC which in turn means less fuel/air and OIL mixture into the crankcase/bearings and cylinder walls. In short plugging up the exhaust, as has been done here, will result in less noise for sure but it also starts a chain reaction of other events that eventually will lead to the demise of the engine and less power/fuel economy in the short term.

J Tiers
05-17-2009, 12:34 PM
That makes no sense. They have to get there through a fixed hole in a fixed time from a fixed cylinder volume at a fixed rpm.

That is where your mistake lies Jerrry. The time involved hasn't changed. The engine is still running at the same RPM so the time allowed for the exhaust to leave the system is the same but the orifice is much smaller. That translates directly to higher pressure, higher temperature and higher wear.


No mistake, at least not on MY part..... YOU have a fundamental error.

Please read what I wrote, and you MAY begin to understand before you go off without thinking.

WHAT IS THE TIME?

EITHER

A) the smaller time the ports are open (if restriction is at the block port)

OR

B) The entire time between exhaust pulses (if restriction is after a large averaging volume

You seem to find no difference between these times, but later you claim averaging..... Please make up your mind which argument you want to use, as they are somewhat mutually exclusive.





Nope. No ignoring going on. At least, not by me OR Doc.

Whatever you say...... but you certainly are wrong..... and you will STILL be wrong so long as you ignore basic principles of physics and engine operation



That might be true if I had installed the restrictor directly on the exhaust port of the engine. Apparently you haven't noticed the size of the muffler that lies BEFORE the restrictor. It is plenty large enough to average the pressure before it gets to leave by the restrictor and there will be no appreciable difference between adding a restriction as I did or as the OP did except the size of the restriction.

[edit]

I can't figure out why you are digging yourself such a deep hole Jerry?

The muffler volume is almost certainly far lower than the volume needed to really average..... but if you want to talk about that in detail...... then

Please state the internal volume OF THE FIRST CHAMBER of the muffler, and compare that to the volume of exhaust gases at atmospheric pressure. Note the passage size between chambers.

Tell us the results.

Nope, I am NOT digging a hole..... But YOU may be

If the muffler that exists is large enough to average , it would also be more effective in reducing sound levels. But apparently significant pulsing exits the existing muffler.

I said that I don't have the numbers for his unit...... but there WILL BE a suitable combination, and the hole will be quite a bit smaller than the port cross-section. Will it be 0.140"? Probably not. I would expect it to be larger, and I would compare it to the venturi........

I stated that his setup may not be nearly so bad as you predict, due to what appears to be a substantial volume of chamber. I have never said its a great idea to put in a pinhole exit....... Just that there are better and worser ways to do it, and his appears to be the not as bad way.

And, there is certainly a difference in peak and average backpressure.

PEAK backpressure is a direct restriction on both exhaust pressure release, and scavenging.

AVERAGE backpressure, unless extreme, is a restriction primarily on scavenging, since the scavenging pressure is low, directly derived from atmospheric, without added combustion pressure, but the combustion pressure is considerably higher than any reasonable average backpressure..

A chamber, with or without small hole, after the existing exhaust, will allow lower peak backpressures than screwing the restriction directly into the muffler, or the block. The size of that chamber affects how close to atmospheric the muffler exit "looks" to the exiting pulses.

Your own test showed hotter, which would be expected, but not drastic engine-killing heat, by your own statement.

J Tiers
05-17-2009, 12:37 PM
That just does not make much sense past a couple of engine revolutions, That tiny hole will cause a restriction regardless of the pipe. After the first couple of revolutions the pressure will build in the pipe and then you are back to square one, if the exhaust is discharged into any kind of pipe, muffler or whatever and can only eventually exit by that tiny orifice then back pressure will certainly be the end result.


Your error is not to realize the difference between peak and average backpressure.

The "built up" backpressure is average........ if the hole were in the port, it would develop PEAK backpressure.

Every muffler has backpressure. They are, or should be, designed specifically to average the flow, because only in that way can the pulse noise be "muffled"....

airsmith282
05-17-2009, 12:50 PM
OK time for the specs

the muffler ID on the output hole is 11.65MM
I made a 14 MM hole in my inlet where it attachets to the muffler out port
also uses a set screw to make positive lock up seal ...

the collar is in debth withthe 14.,,, hole 41.21 MM Deep then at that point the exhaust wil expand in the chamber that has an ID of 26.57 MM wiht a length of 7 and 1/4 inchs long, the front cap that has the 9/64 hole drill in the front has a total depbth of 15.02mm the second bottem hole for venting is 1/8 and its driled into the hollow area of the tube 17.84 mm from the front edge of the tube it self.. the OD of the tube it self is 33.40 mm .. iam not sur hte grade of aluim it was just some every day stuff i ask the shop for nad it just a wal thickness of 3.70 MM

Note the front and back fittings are made of 316 SS and are hammer fittited into the tube extream tight fit totaly air tight and not removable after assembled .. the set screw i used was an m4x.07
now these are the specs of the device i built..

now if you can prove me to be incorrect and that its going to harm the engine in anyway you know how the specs and you have pics as well so build one and let hear your results..
keep in mind you have to have the same generator as well.. and you must build this thing to the exact specs i have listed...

Evan
05-17-2009, 01:32 PM
Jerry, look at the picture of the exhaust system. The muffler is plenty large enough to average the exhaust pressure. That is why the genset isn't noisy in the first place.


EITHER

A) the smaller time the ports are open (if restriction is at the block port)

OR

B) The entire time between exhaust pulses (if restriction is after a large averaging volume


What? Neither of those will change if the RPM remains constant. Would you pleast explain how the time between exhaust pulses can change if the rpm doesn't? That would be an interesting trick.

I suggest you take a break Jerry, you aren't thinking things through this morning.



You seem to find no difference between these times, but later you claim averaging..... Please make up your mind which argument you want to use, as they are somewhat mutually exclusive.


DAng. There is no difference in the times. You brought up averaging and there is enough volume to average the pressure. SO WHAT???

ALL I did was compare muffler as is to muffler with smaller hole, and not that much smaller compared to OPs "solution". The point was to show that even a mild restriction will raise operating temps.

J Tiers
05-17-2009, 02:17 PM
So you are saying that if the hole is the same size but in a different location then more exhaust will fit through it? How does that work?

Because there is more time available, the "farther" the hole is volume-wise from the main exhaust pulse




What? Neither of those will change if the RPM remains constant. Would you pleast explain how the time between exhaust pulses can change if the rpm doesn't? That would be an interesting trick.

I suggest you take a break Jerry, you aren't thinking things through this morning.


SIGH.....

Who said the time changes? Not me....

The exhaust pulse length, and the timing between pulses are different animals. because exhaust is obviously not open for the entire cycle, but only a shorter portion of it.

The pulse length is the time the exhaust is open.... Actually the HIGH PRESSURE pulse is the time only exhaust is open, and the low pulse is the time both exhaust and admission are open (scavenging).

A restriction near the port, or before sufficient volume to absorb the exhaust gases without a rise well above atmospheric, restricts the exit of the high pressure pulse of exhaust before admission opens. It will also affect scavenging.

The time between pulses is the time that a larger volume* (SUFFICIENT to absorb the high pressure exit of exhaust) has to leak down towards atmospheric. The average pressure affects the scavenging more than the high pressure exhaust initial pulse, by the difference between scavenging pressure and back pressure. if the volume is large enough to absorb the high pressure pulse, it will absorb the scavenging pulse also, without a spike in pressure.

From the OP's statement, the muffler doesn't work very well, and without testing one of those, which are probably illegal to sell here, the assumption is that the averaging isn't really very good.

In that case, adding a volume after the existing poor muffler can improve the noise..... and depending on the exit hole, may not have such a drastic effect.

Depending on relative volumes, the test you did may be non-representative. if the noise is considerably different, the direct assumption is that the external pipe has a significant added effect on averaging.

There is certainly a chance that the restriction is so drastic that the reduction in noise is due to only a tiny new charge reaching the cylinder.... but the power output seems to be there, so presumably that isn't the main effect.

Without NUMBERS on volumes etc, neither you NOR I have the information to say this absolutely will or will not happen. Your test apparently didn't show that much temp rise, and it was at best approximately representative, but on the "worse case side".

If you want to assert that there is already plentyo of volume, you need numbers

The "whole" (hole?) thing has electrical analogs....... in filter design, and power supply smoothing.

*any volume, actually, but it may not matter for insufficient volume.

radkins
05-17-2009, 04:52 PM
Your error is not to realize the difference between peak and average backpressure.

The "built up" backpressure is average........ if the hole were in the port, it would develop PEAK backpressure.

Every muffler has backpressure. They are, or should be, designed specifically to average the flow, because only in that way can the pulse noise be "muffled"....


No error here, I am quite aware of what you are talking about but with a muffler that size that principle would only allow for lower back pressure at a VERY low RPM with an exhaust port that small.

radkins
05-17-2009, 04:59 PM
Because there is more time available, the "farther" the hole is volume-wise from the main exhaust pulse

The distance will not matter after the first few revolutions and this is what I was talking about earlier, it is the TIME it takes for the exhaust to exit this tiny hole that is going to make the difference. If pressure remains from a previous exhaust cycle, which it will in this case at operating RPM, then the next exhaust cycle will have to exit the port into a pressurized muffler (back pressure).

J Tiers
05-17-2009, 05:23 PM
The distance will not matter after the first few revolutions and this is what I was talking about earlier, it is the TIME it takes for the exhaust to exit this tiny hole that is going to make the difference. If pressure remains from a previous exhaust cycle, which it will in this case at operating RPM, then the next exhaust cycle will have to exit the port into a pressurized muffler (back pressure).

Quite right.

But the key issue is HOW MUCH the pressure DROPS before the next exhaust pulse, or actually, what the residual pressure is.

it is considerably different if the high pressure exhaust has to get out that hole during the "exhaust open" time, vs having a whole cycle to do it.

Each volume will have a different response to the high pressure pulse, and each hole size will have a different "leak down time".

They are somewhat disconnected, but higher pressures do leak off faster than lower pressures.

In this case, for the effect of that added chamber and hole, it makes a difference how big the existing muffler is vs the exhaust gas volume..... and how much gas can get through the hole in a full cycle at the average backpressure.

I don't know those numbers, but it is possible that the way he has it set up the total effect is not as bad as it has been made out to be, in terms of "instant motor death". Evan's measurement was not so dire as the original predictions, and his case was not truly representative, worse than the actual, in terms of initial expansion volume, and hence peak backpressure.

radkins
05-17-2009, 05:45 PM
Quite right.

But the key issue is HOW MUCH the pressure DROPS before the next exhaust pulse, or actually, what the residual pressure is.



In this case, for the effect of that added chamber and hole, it makes a difference how big the existing muffler is vs the exhaust gas volume..... and how much gas can get through the hole in a full cycle at the average backpressure.


You are thinking of only one exhaust cycle or maybe two. If there is residual pressure, due to the restrictive exhaust hole, from the previous exhaust cycle it will be cumulative with each succeeding cycle. You are correct in that as the pressure rises it will drop at a faster rate between pulses but this rate of drop will decrease as the pressure falls, plain and simple if the exhaust is coming into that muffler faster than it can exit from that small hole then there will be back pressure after a few revolutions no matter how much volume the muffler has.

I see what you are saying and I can see your reasoning BUT I also see the flaw. At operating RPM there is simply going to be more exhaust enter that muffler than will be able to exit until the pressure rises to a point that the exit rate balances with the exhaust entry rate into the muffler. At a very low RPM there might be time enough for the exhaust pressure to drop between pulses but as the RPM increases the gas will only exit at a higher rate after the pressure increases, this is what will cause the back pressure.

Evan
05-17-2009, 05:59 PM
Because there is more time available, the "farther" the hole is volume-wise from the main exhaust pulse


What? No there isn't. The flow rate through an orifice is pressure dependent. Put it further away so that there is some additional resistance between it and the source and you will have a lower pressure at the orifice and a lower flow rate and therefor HIGHER PRESSURE since the resistance will act as an ADDITIONAL RESTRICTION.

David Powell
05-17-2009, 07:32 PM
I have " played" a bit with various schemes to quieten both compressors and gas engines for various reasons. One point which i feel may have been forgotten by those who seem horrified by my northern pals muffler is that the amount of restriction by a small orifice depends greatly on its length,take a piece of 1/8" plate and drill a 1/8" hole through it, then blow through it. Next take a piece of straight copper pipe with a bore of 1/8" and 6" long, now TRY to blow through that, it feels like about 100 times the restriction. Obviously, if the engine revs fall off dramatically when you screw a home made muffler on then you have made it more restrictive than it should be, however, if the revs remain the same, or perhaps just fall very slightly and the exhaust quiets down then surely you are pretty near success. Incidentally, I size blast nozzles for my model steam engines this way, though I would add that they are tapered in both directions, so the actual length of the parallel part of the nozzle is very small, indeed often there is no parallel part, the two tapers running into each other, In small sizes thous count,probably in Airsmith's case 1/16 ths difference in hole sizes matter.Many modern machines owe some of their success to development of an" odd "idea first tried out by a " backyard tinkerer", so lets not just look for what is wrong with another fellows ideas, and experiments , and make ourselves feel important and self righteous by criticism but lets see what is good about them and try to back them up and perhaps suggest how to improve them.Ok I would also like world peace and honest politicians, regards David Powell.

radkins
05-17-2009, 07:39 PM
The "distance to the exhaust hole" concept simply does not apply here because the "muffler" is too small to be used as an expansion chamber and the hole is just that, a hole or orifice in one wall of a small chamber that will contain the gases from the exhaust port and not a tube to increase exhaust velocity.This idea that some back pressure is needed to make the engine run efficiently is a mis-conception based on the fact that some two stroke engines have baffling in the exhaust, however simply adding baffles or reducing the size of the exhaust hole will only add back pressure. In a PROPERLY ENGINEERED tuned exhaust a smaller exhaust can be used to actually reduce back pressure instead of increasing it but this is done using a tube and not just reducing the size of the hole. If exhaust gas is forced into a smaller pipe after exiting the exhaust port it will increase in velocity as it travels through this smaller tube as the pressure increases. Then as the pulse comes to an end and the pressure drops the gas will tend to continue traveling at a high rate because of inertia, the gas has mass and the faster it travels through the pipe the harder it is to slow or stop it. If the exhaust gas is moving fast enough it will then create a negative pressure on the exhaust port as the piston slows thus increasing the scavenging effect of the cylinder. This negative pressure will have the effect of literally vacuuming out the remaining exhaust from the cylinder and creating a negative pressure in the cylinder as the intake port is exposed thus insuring a more complete cylinder charge with fresh fuel/air. If this occurs too low in the RPM range the vacuum effect from the high velocity gas exiting the exhaust can actually "suck out" not only the exhaust but also part of the incoming fuel charge. The use of baffling and/or sizing of the exhaust tubing can be used to slow down the exhaust velocity so that the exhaust/fuel charge timing occurs at a suitable time in the RPM band for the task the engine is designed for. Using a small high velocity tube with baffling is desirable for a bike engine, and also most other uses, because the baffling also tends to have a muffling effect. This gets far more complicated when an expansion chamber is incorporated into the exhaust system to use the expanding gases to also control the exhaust/fuel charge timing and it is not simply a matter of reducing the size of the exhaust hole. On a system such as this length and diameter are very important but it is something that must be engineered for the case at hand and it can not be something as small as we have been talking about here. Many high performance bikes have benefited from a do-it-your-self system but this involves taking into consideration all the factors and a lot of trial and error to get the power where they want it.

The bottom line is that simply adding a foot or so of 1" pipe and choking down the exhaust hole will accomplish none of this and will serve only to increase back pressure and engine temperature and decrease engine life and fuel economy.

radkins
05-17-2009, 07:45 PM
Obviously, if the engine revs fall off dramatically when you screw a home made muffler on then you have made it more restrictive than it should be, however, if the revs remain the same, or perhaps just fall very slightly and the exhaust quiets down then surely you are pretty near success.


David you are missing the fact that the engine in question has a governor on it which will try to maintain the RPM at a predetermined setting even with the exhaust restriction. There is no doubt that if that engine was on a fixed throttle setting the RPM would most certainly drop when that "muffler" is added.

airsmith282
05-17-2009, 07:53 PM
personaly after reading all this stuff sence my pics and specs posted.. iam getting a bad headache just ate the last of the advil in house,, any how you guys have the pics and the specs to settle this 1 or 2 guys for sure need to build the device i did and do the test it on the same generator as i have built it for and give us your results ,,worse case you all learn something new perhaps i will learn one of 2 things i did bad or i did awesome. to argue this and that and back and forth is really getting no where here, as stated what man has learned in the last 100 or so years really is very little and we learn new crap every day...

jdunmyer
05-17-2009, 08:01 PM
Everyone except AirSmith is convinced that he's not saving any money by generating his own power. Me included. But, here's something to chew on:

My cousins ran a pallet shop for many years, and one of the machines is a gang resaw that cuts "cants" (4"X6"s) into boards. Originally, the saw came with 2, 150 Hp motors, one for each arbor. In their original setting, they had no 3-phase power available, so they fitted a Cummins truck engine to drive the arbors and a RPC to drive the feedworks. When they moved their shop to a location with 3-phase power, they had the power company estimate their power usage. It came to $1300.00/month, vs. the $250.00 that they were spending on Diesel fuel. They stuck with the Cummins.

Recently, within the past couple of years, the new owners of the pallet shop had the power company re-estimate the cost of running electric motors. I forget the numbers, but it was several thousand $$$/month, and they are still spending only hundreds/month on Diesel fuel.

Even amortizing the cost of rebuilding/replacing the engine every few years, they're way ahead "making their own power".

I still find it a bit hard to believe.

AirSmith, I'll be interested in seeing just how much you cut your hydro bill by using this generator, vs. the $$$ you spend in gas and oil. Bear in mind that if you're like most of us, your usage is variable enough that it'll take at least several months to tell what's going on. My own usage drops dramatically from Winter to Summer; my bill has gone from about $120.00 to $90.00 in just the past month, and it should decline to $70.00 or so in mid-Summer if we're not running the A/C.

Evan
05-17-2009, 08:11 PM
A commercial shop doesn't pay for power the same way a home user does. Commercial users must pay a "demand charge" which is a charge based on their peak usage during the billing period. It isn't related to how much power they consume but rather on how much generating capacity the utility must have to satisfy their peak demand. Demand charges can be very high if your peak demand is high, even though your total consumption may be very low.

philbur
05-17-2009, 08:12 PM
In theory yes but the frictional loss for the short length of pipe is negligible compared to the small orifice on the end. So if you double the volume by doubling the pipe length the increase in back pressure is also negligible.

Flow resistance for pipe: Kp=fL/D - where f is the friction factor, which for 1” pipe is something like 0.019

Flow resistance for a sharp edged orifice: Ko=2.6

Then you have to correct for diameter so the equivalent flow resistance of the orifice at the pipe diameter =Ko*Dp^4/Do^4

So for the example under discussion:

Flow resistance for the pipe Kp = 0.11
Flow resistance for the orifice Ko =6,600

So doubling the volume by doubling the length of pipe would increase the flow resistance (read back pressure) by 0.0017%

Phil

PS: Rounding or tapering the exit from the orifice would greatly reduce it’s flow resistance.

What? No there isn't. The flow rate through an orifice is pressure dependent. Put it further away so that there is some additional resistance between it and the source and you will have a lower pressure at the orifice and a lower flow rate and therefor HIGHER PRESSURE since the resistance will act as an ADDITIONAL RESTRICTION.

Evan
05-17-2009, 08:14 PM
The point is that it will NOT reduce the resistance at all no matter how large the volume or how far the distance, as your calculation shows.

philbur
05-17-2009, 08:36 PM
But he didn't say it would reduce the resistance what he did say was that it will give more time.


The point is that it will NOT reduce the resistance at all no matter how large the volume or how far the distance, as your calculation shows.

philbur
05-17-2009, 08:50 PM
When I was much younger I use to mess with 2 strokes going the other way. A learner 2 stroke MC had a restrictor in to limit the horsepower in order to reduce the rate at which teenagers killed themselves. So the trick was to remove the restriction and change the carburettor jetting in order to get more power. Without the re-jetting it would run too rich with all that that entailed. So I guess the reverse is true. If you add a restriction it will run lean with all that that entails, namely reduced power and higher temperatures. Whether the modification results in disaster only time will tell. Exhaust dynamics of 2 stokes is not rocket science and is well understood so I think the possibility that a simple new improvement has been discovered is extremely low.

Phil

airsmith282
05-17-2009, 08:51 PM
umm i gota me and idea i got more of the hollow aluim left goingto see what it does and compare to the one i made already ,, the wheels are turining in the head ideas are flowing ,, then next idea once perfection has been met will be a short length but rather large OD model to have the same volume allow able but with only down ward exit holes instead of a frontal exit hole ..


wound if i can make my lawn more work as efficent as well but alot more more quiet ?????

radkins
05-17-2009, 09:30 PM
But he didn't say it would reduce the resistance what he did say was that it will give more time.


And that makes zero sense after a few revolutions. If the rate at which the exhaust is entering the "muffler" is higher than the exit rate through that small hole then back pressure WILL result regardless of the muffler volume! OK, it's given that the exhaust is exiting full time through that hole at a rate dependent on exhaust pressure so the theory is that it will have "time" to exit during the compression/power cycle during which time there will be no input from the exhaust port. This might work at a very low RPM but at engine operating RPM the incoming exhaust gas will be at a higher rate than will pass through that tiny hole over any given time period, in any case the length of the pipe would not have much effect on it since the residual exhaust will be cumulative. After the first exhaust cycle if the gases are not completely discharged, which they will not be from that tiny hole, then the incoming gases from the next cycle will add pressure to what's still there and no matter how long the pipe is this is still going to happen. Fellows the gas HAS to go somewhere and if it is coming in at a rate higher than can pass through that hole it is simply going to pressurize the pipe and making it longer will only add more volume of pressurized exhaust gas, what has been done to that generator simply defies logic and almost everyone here can see that! No matter how long or big the pipe is or where the hole is located if the exhaust is coming in faster than it can exit that hole, which it most assuredly will be, then back pressure will increase until the exiting gases and incoming gases balance out due to increased exit flow rate from the higher pressure.


I agree that test does not appear to exactly duplicate what was done BUT from the description the test also appears to have even less restriction which would mean that it would have even fewer problems. Airsmith I honestly think that if you were to check that thing with an IR thermometer you would find that little engine is running on the ragged edge. For sure choking down the exhaust will quieten an engine but if it was as simple as doing that they would come from the factory that way. The fact is the factory has to make a compromise between noise and performance otherwise all these generators would be whisper quiet if it was just a matter of reducing the size of the exhaust hole.

David Powell
05-17-2009, 09:34 PM
David you are missing the fact that the engine in question has a governor on it which will try to maintain the RPM at a predetermined setting even with the exhaust restriction. There is no doubt that if that engine was on a fixed throttle setting the RPM would most certainly drop when that "muffler" is added.
My experiments with mufflers were made mainly to try to quieten a very noisy 4 stroke snowblower. As with the steam engines and their blast nozzles I didn.t just give it one try at one set of revs, but under all circumstances possible, from tickover to overreving with the governor propped open. ( if you have ever heard or seen a Saunderson tractor running with a propped open governor you would know what lack of governor control excitement really is but thats another story). It is very hard for the average experimenter to test properly , very often the reported results are only subjective impressions and not objective quantified reports. Screwing experimental mufflers off and on to screaming little engines with asbestos gloves while outside in a snowstorm takes a lot of devotion and determination, so I only did it until I was satisfied that the neighbours would not lynch me for blowing the driveway before I went to work.( No one has ever said I am sane) regards David Powell.

jdunmyer
05-17-2009, 09:55 PM
A commercial shop doesn't pay for power the same way a home user does. Commercial users must pay a "demand charge" which is a charge based on their peak usage during the billing period. It isn't related to how much power they consume but rather on how much generating capacity the utility must have to satisfy their peak demand. Demand charges can be very high if your peak demand is high, even though your total consumption may be very low.


Evan,
The numbers that I remember from years ago were: $400.00/month for demand charges, $900.00 for the actual electricity, total $1300.00/month.

Still, they were much better off making their own power. Remember, the estimates came from the power company, and even if they were off by 100%, real numbers being half the estimate, there was still no question.

airsmith282
05-17-2009, 10:41 PM
if i wanted to i could get a 400 watt wind generator and then no gas to worry about just need wind all the time,

Arcane
05-17-2009, 10:55 PM
Just to add a bit to the conversation from someone in the electrical line trade and district office for 35 years here in Saskatchewan, I have seen a few companys that figured they could do it cheaper, and tried. They set up their own generation and went at it, but without an exception they ALL sooner or later hooked onto the grid. It was a monetary decision for them....

bborr01
05-17-2009, 11:23 PM
if i wanted to i could get a 400 watt wind generator and then no gas to worry about just need wind all the time,
If you are planning on much power from this wind generator, I hope you have a lot of wind. I used an air-x 400 wind generator last winter to (help) charge my RV batteries. You need about 20mph winds to get any real power. At 35 mph I would get 40 amps at 12 volts. At 20mph I was getting about 5-7 amps. You need lots of wind.

J Tiers
05-18-2009, 12:20 AM
You are thinking of only one exhaust cycle or maybe two. If there is residual pressure, due to the restrictive exhaust hole, from the previous exhaust cycle it will be cumulative with each succeeding cycle.

Not indefinitely, there is a balance pressure where it stops. As you yourself admit, there will be such an equilibrium point, at a higher-than-zero backpressure, which is the 'average" backpressure I described.

It will be higher than with NO restriction, but LOWER with the restriction after an expansion volume and higher with no expansion volume. This is because with NO expansion volume, all the pressure pulse AND scavenging flow has to go through the hole in the time the ports are open, and the peak pressure will be very high, dragging up the average. Potentially a lot of exhaust will be retained, and the engine may not run.

if allowed to expand into some volume, the exhaust will scavenge, but after some time, as I mentioned in a prior post, and you reiterate, the pressure will rise to a new average backpressure, which will inhibit scavenging more or less depending on how high it is.



I see what you are saying and I can see your reasoning BUT I also see the flaw. At operating RPM there is simply going to be more exhaust enter that muffler than will be able to exit until the pressure rises to a point that the exit rate balances with the exhaust entry rate into the muffler. At a very low RPM there might be time enough for the exhaust pressure to drop between pulses but as the RPM increases the gas will only exit at a higher rate after the pressure increases, this is what will cause the back pressure.

Well we don't know that balance point. You are however, quite correct that there has to be a rise in average backpressure to an equilibrium point where the pressure gives just enough flow to handle the exhaust volume. That point varies with loading and throttle position, as you point out.

It could be that the hole airsmith has is big enough to work in his conditions. Must be, since the engine runs. but we don't know how well it runs, there is zero instrumentation. We don't know the temp or the backpressure.

I agree it seems small. But it may not be 'too" small, depending on the engine gas flow at the existing loading. And a slightly larger hole might give the same performance sound-wise, with less restriction and a lower average backpressure.

We have Evan with a somewhat different setup, which appears to have a not-totally-horrible (by his own admission) temperature rise. He has a larger hole, but less expansion volume. We don't know how that balances. So it's possible that airsmith's setup might not be 'automatically" so bad, which is my point.

And, it isn't as if the existing muffler has zero backpressure.

BTW, the point about the tube vs the sharp orifice.....

The sharp orifice is actually pretty bad........ it causes a contraction of the flow to a size under the actual hole size.........

if you put a lead-in and lead-out curves on it, as often seen on ventilation fans, that contraction is avoided, and the pressure drop in the orifice is reduced quite a bit. The effect of better flow on the sound attenuation I can't comment on.


If you are planning on much power from this wind generator, I hope you have a lot of wind. I used an air-x 400 wind generator last winter to (help) charge my RV batteries. You need about 20mph winds to get any real power. At 35 mph I would get 40 amps at 12 volts. At 20mph I was getting about 5-7 amps. You need lots of wind.

The rule is half speed is 1/8 power (cube root of speed change). That's a big hit to take, and is why nearly every small wind turbine is an economic failure. You need a farm of big turbines, in a good wind area, to make it pay.

We are doing some consulting design of wind turbine systems for some small power guys, and we can't figure out how they expect to get a payback...... the numbers just are not there with the cost of equipment and installation. Ditto for some trash-to-energy folks we are working for (well not now we aren't, they are not paying their bills!).

Evan
05-18-2009, 12:23 AM
Still, they were much better off making their own power. Remember, the estimates came from the power company, and even if they were off by 100%, real numbers being half the estimate, there was still no question.


Most people including a lot of accountants don't calculate the costs correctly. Naturally you can't just count the ongoing cost of fuel. You have to allow a certain amount per hour of operation for maintenance and repair. That isn't all though. To do it correctly you also need to account for the capital cost of equipment and installation and how it was paid.

If paid cash then you must calculate how much that cash could have made in investment experience if that capital cost was avoided by hooking to the grid. You also then must assign a dollar per hour value to that initial capital outlay based on the expected lifetime of the equipment. You also must take into account any machinery and equipment taxes that may be levied in your jurisdiction. You should also count any additional cost incurred by not having that capital available for use, such as the cost of running a line of credit where the those costs cannot be clearly apportioned to other items.

If financed then you must count the cost of borrowing as well as amortizing the capital cost over the repayment term and also count how much that borrowed money could have made if reinvested in either a capital gain investment or an interest bearing investment.

In short, any and every relevant cost and lost investment opportunity must be charged to the the cost of generating that power. Those hidden costs will normally far exceed the ongoing operational cost of making a kilowatt hour of power.

airsmith282
05-18-2009, 12:24 AM
If you are planning on much power from this wind generator, I hope you have a lot of wind. I used an air-x 400 wind generator last winter to (help) charge my RV batteries. You need about 20mph winds to get any real power. At 35 mph I would get 40 amps at 12 volts. At 20mph I was getting about 5-7 amps. You need lots of wind.


i was joking about the wind generator iam well aware how crappy they are..

airsmith282
05-18-2009, 12:26 AM
Most people including a lot of accountants don't calculate the costs correctly. Naturally you can't just count the ongoing cost of fuel. You have to allow a certain amount per hour of operation for maintenance and repair. That isn't all though. To do it correctly you also need to account for the capital cost of equipment and installation and how it was paid.

If paid cash then you must calculate how much that cash could have made in investment experience if that capital cost was avoided by hooking to the grid. You also then must assign a dollar per hour value to that initial capital outlay based on the expected lifetime of the equipment. You also must take into account any machinery and equipment taxes that may be levied in your jurisdiction. You should also count any additional cost incurred by not having that capital available for use, such as the cost of running a line of credit where the those costs cannot be clearly apportioned to other items.

If financed then you must count the cost of borrowing as well as amortizing the capital cost over the repayment term and also count how much that borrowed money could have made if reinvested in either a capital gain investment or an interest bearing investment.

In short, any and every relevant cost and lost investment opportunity must be charged to the the cost of generating that power. Those hidden costs will normally far exceed the ongoing operational cost of making a kilowatt hour of power.

EVAN what the hell does this have to do with the device i made ?????????????????????????????????????????????????? ?

Evan
05-18-2009, 12:30 AM
It has to do with what you spend your money on. You can buy utility power for around 8 cents per kilowatt hour. Your genset will cost much more than that to make power and that money could be spent on new tools instead.

J Tiers
05-18-2009, 12:34 AM
EVAN what the hell does this have to do with the device i made ?????????????????????????????????????????????????? ?

It has to do with you NOT getting a better deal on your power from genset than from powerco, long term.

Your low cost of equipment helps, but if you account right, you should put aside the cost of a new one at full retail over the time that one lasts..... and charge it to the cost of generation.

I WILL say that if you cost account right, you can probably find a net loss in picking up found money........

Lawyers and cost accountants can kill any deal. The movie studios have done it for years.... according to them, every box office hit has been a net loss to the studios....... because they don't want to pay residuals.

But even with that, you just are not gonna win out cost-wise, even if you maybe are not actually gonna kill your engine in 3 hours.....

Sparky_NY
05-18-2009, 06:01 AM
A commercial shop doesn't pay for power the same way a home user does. Commercial users must pay a "demand charge" which is a charge based on their peak usage during the billing period. It isn't related to how much power they consume but rather on how much generating capacity the utility must have to satisfy their peak demand. Demand charges can be very high if your peak demand is high, even though your total consumption may be very low.

And..... starting 2 150hp motors on that machine would make for a very high peak demand reading on a meter

J Tiers
05-18-2009, 08:48 AM
And..... starting 2 150hp motors on that machine would make for a very high peak demand reading on a meter

Nope.

The demand charges are nearly always for your highest 15 minute or 30 minute demand.... not the highest peak pulse of current that is ever seen.

Starting a motor of 150HP won't affect it, but running that motor will.

tryp
05-18-2009, 08:53 AM
The truth came out a dozen posts ago.

Airsmith was the victim of a legal corporate scam that is common in Ontario. He mentions he pays for his electric utility through a third party. In case no one is familiar with this scam here in Ontario we have a regulated utility, they make cheap power and are alowed to make a certain profit and no more.

These third party companies are incorporated and they employ salespeople to go around door to door scaring people into thinking the power rates are going to skyrocket so they should sign contracts for their power from them. Airsmith pays .20 cents per kW/h plus the base charges 25-40? dollars.

Airsmith I hope you are right and you got that contract dropped cause you got soaked. Your bill with ontario hydro will be much better, and if you do the simple math 5 bucks you spend on gas will last you 100 hours if you were paying 6 cents per kW/h asssuming a 800W load.

But you came to terms with the economy already.

But you won't let go of the muffler thing, you didn't invent anything new and might I suggest taking a correspondance course in fluid dynamics.

Evan
05-18-2009, 08:55 AM
I have seen demand power meters that have a red needle which is a peak reading indicator. It is pushed up and stays there until the meter is unlocked and the needle reset when it is read. I don't see how a timed reading can be involved. It would be peak only.

Evan
05-18-2009, 08:59 AM
I never heard of that particular scam. As far as I know it doesn't exist in BC. That should be illegal if it isn't already.

radkins
05-18-2009, 09:59 AM
Not indefinitely, there is a balance pressure where it stops. As you yourself admit, there will be such an equilibrium point, at a higher-than-zero backpressure, which is the 'average" backpressure I described.

It will be higher than with NO restriction, but LOWER with the restriction after an expansion volume and higher with no expansion volume. This is because with NO expansion volume, all the pressure pulse AND scavenging flow has to go through the hole in the time the ports are open, and the peak pressure will be very high, dragging up the average. Potentially a lot of exhaust will be retained, and the engine may not run.

if allowed to expand into some volume, the exhaust will scavenge, but after some time, as I mentioned in a prior post, and you reiterate, the pressure will rise to a new average backpressure, which will inhibit scavenging more or less depending on how high it is.



Well we don't know that balance point. You are however, quite correct that there has to be a rise in average backpressure to an equilibrium point where the pressure gives just enough flow to handle the exhaust volume. That point varies with loading and throttle position, as you point out.




Of course it would be unacceptably high without any expansion volume but no one even assumed that and we are talking about adding volume, anything over the total volume of the incoming gases is what will not matter. Even the expanding gases will not matter because pressure will build in the muffler itself as the rate of the incoming exhaust exceeds the exit rate. Besides it is the equilibrium point that you mention that is the problem. When the pressure must rise in order for the incoming and exiting gases to reach this balance point then that is the back pressure we are talking about! You are saying now exactly what I have been trying to get across but the difference seems to be that you feel this will not hurt anything. The fact is that even the factory muffler is going to have some restriction and I think most everyone will agree with that so reducing the size of the exhaust hole would increase this restriction, adding the extra length of pipe for more volume will not solve the problem for a very simple reason. While the peak pressure of exhausting into a small volume would immediately cause problems the fact still remains that because of the increased restriction the gases are escaping at a lower rate than the incoming exhaust so pressure will build up until a balance is reached, this is going to be much higher than it would if the opening was the same size as the factory opening. Since the factory muffler in all probability has enough volume to contain the cylinder volume, or nearly so, then adding the extra length of pipe will not drop the peak pressure dramatically. Any drop in peak pressure will be offset by the increased back pressure that is going to build up in the muffler and added pipe. The bottom line is that no matter how much volume there is for the gas to expand if the volume of gas entering the exhaust exceeds the exit rate over a given time period then back pressure will result up to the balance point and this balance point is the problem not the peak pressure. I am not saying peak pressure is no concern just that the back pressure that is going to be required to overcome that tiny restriction is going to be more than enough to cause major problems.

airsmith282
05-18-2009, 10:28 AM
The truth came out a dozen posts ago.

Airsmith was the victim of a legal corporate scam that is common in Ontario. He mentions he pays for his electric utility through a third party. In case no one is familiar with this scam here in Ontario we have a regulated utility, they make cheap power and are alowed to make a certain profit and no more.

These third party companies are incorporated and they employ salespeople to go around door to door scaring people into thinking the power rates are going to skyrocket so they should sign contracts for their power from them. Airsmith pays .20 cents per kW/h plus the base charges 25-40? dollars.

Airsmith I hope you are right and you got that contract dropped cause you got soaked. Your bill with ontario hydro will be much better, and if you do the simple math 5 bucks you spend on gas will last you 100 hours if you were paying 6 cents per kW/h asssuming a 800W load.

But you came to terms with the economy already.

But you won't let go of the muffler thing, you didn't invent anything new and might I suggest taking a correspondance course in fluid dynamics.

hello TRYP i wont let the thing go your right on that but no one is willing it seems to back up there claims that what i built and added onto the existing muffle will cause damage to my genney, see there is no text book written for what i have done, sure nothing new invented so how come it seems iam the only one that s gots one, or even thought of such a thing ..

i dont need a course in fluid power i have enough of an understading of the subject as it is that its like anything else , i dont belive the books till i try it for my self if it works out, then great if it does not then i guess i gota go back to the drawing board again and try a different approch..over the years with alot of different stuff i have proven the books to not be so right, inmany areas and i have also proven what most said you cant this or you do that will guess what i was right they were wronge, now if any one cares to prove me wronge and what i have done here is going to damage the machine the please step and and prove it beyond a shadow of a doubt ,and ill back off and remove said device and accept the fact i was wronge..

but that dont mean iam going to give up ill try a different approch, i need to make thing thing quieter and at the same time not cause harm to the machine, now some one said if it was possible it would have been done at the factory well you ever thing that A: it could have raised the cost to high or B: how about they thought about it but decided that keeping it the way it is was best and would sell better if it remaied a cube like it is..

anyhow there you go

Evan
05-18-2009, 11:40 AM
but no one is willing it seems to back up there claims that what i built and added onto the existing muffle will cause damage to my genney

That is exactly what my test does (back up my claims). I am not willing to restrict the exhaust to the same degree you have since it will probably cause damage in even a short period of operation.

If you really want to make the genset quiet without damaging it then bury a 20 litre metal pail in the ground with a tube the same size as the bung sticking out fitted with a 180 degree elbow so it turns down for the outlet. Feed the exhaust into the pail with a pipe of the same or larger diameter as the port on the muffler.

airsmith282
05-18-2009, 12:54 PM
That is exactly what my test does (back up my claims). I am not willing to restrict the exhaust to the same degree you have since it will probably cause damage in even a short period of operation.

If you really want to make the genset quiet without damaging it then bury a 20 litre metal pail in the ground with a tube the same size as the bung sticking out fitted with a 180 degree elbow so it turns down for the outlet. Feed the exhaust into the pail with a pipe of the same or larger diameter as the port on the muffler.


you experment backs up nothing that has to do with what i built ,it only shows that you restriced the out cooming exhaust right away and that it causes problems. it shows nothing as to the device i made and how it works and if it is a problem causer. you wont convice me or any one unless you can back up what you say , i have however proven that A it does quiet it down a bit more and its enought my neibours wont complain at night when iam in the shop. B i have proven after now oever 20 hours that it has not harmed the motor or the genny at all. you know part of the devolpment of new things is all about risk other wise no one learns anything new .no one knows if it can be done, to many are willing to accpet that the books are right and the rest of us are all wornge well to hell with the books. there not always right and to many times in history people have proven that the books are not so right after all are they now ..

no one knows squat untill they take the step of faith and try something, iam not afraid to try new things cause i want to learn and i want to know i just have to know if something can be done or not.. other wise i learn NOTHING..

no offence man but seems to me like your set in your ways and belive every thing in books that you read ..
oh well guess ill contact the factory that makes the genney and get there opnion on it , might as well goto the guys the designed and built the thing

Evan
05-18-2009, 02:29 PM
no offence man but seems to me like your set in your ways and belive every thing in books that you read ..


That of course explains why I like to do my own experiments all the time.
Sorry, you need to study science. You have a great deal to learn so don't waste time trying to justify a nice looking project in the face of valid criticism. You haven't made a mistake in building it. Your failing is simply not knowing enough. Fortunately that is easy to fix, stupid isn't. Continuing to use it when you have been clearly shown by myself and others why you shouldn't, that is a mistake and may even be stupid.

topct
05-18-2009, 05:05 PM
What does the spark plug look like?

I forgot to ask.

airsmith282
05-18-2009, 06:26 PM
That of course explains why I like to do my own experiments all the time.
Sorry, you need to study science. You have a great deal to learn so don't waste time trying to justify a nice looking project in the face of valid criticism. You haven't made a mistake in building it. Your failing is simply not knowing enough. Fortunately that is easy to fix, stupid isn't. Continuing to use it when you have been clearly shown by myself and others why you shouldn't, that is a mistake and may even be stupid.


well i guess we shall see what the factory says about if its stuip or not or dangerous to the machine or not and thank you but i have a better understanding alot more about things you might think or even know..

airsmith282
05-18-2009, 06:28 PM
What does the spark plug look like?

I forgot to ask.

whats that got to do with anything it looks the same as it did before i added on the device hasent changed it any, still fires up great and runs smooth as glass ..

davidh
05-18-2009, 07:05 PM
and its only physics 101. can't change some folks way of thinking no matter what. . . . . .

on the other hand, my 300 cc snowmachine has a exhaust outlet that only about 1-1/4, maybe 1-3/8 inches in diam. and the muffler/expansion chamber is about 8 inches in diameter. go figure.

i figure if there was a better way to get more usable work out of the engine, the engineers would have done it. . . . . why settle for less if more is available. . . . .

im old but not goofey yet. how the hell can you beat the cost of power from your utility company ? if i could, then i would have a generator running outside my kitchen window.

im trying to not be offensive but geeeeze. . . . .

davidh (the old guy)

AllanR
05-18-2009, 07:15 PM
Airsmith282
Gene has given you a very useful and cheap way of monitoring your motor’s performance.
I believe he was asking what the condition of the spark plug was.
A light tan colour is desirable, indicative of normal operations.
By monitoring the color and type of the deposits on the electrode and insulator you can determine if the engine is running too rich or too lean, too hot or too cold etc.
Check out this link

http://www.gnttype.org/techarea/engine/plugs.html

I hope this helps
Thanks
Al

Evan
05-18-2009, 07:26 PM
It is possible to at least come close to the power company retail cost of power if you do it right. There is a new generation of micro turbines that run on natural gas. They supply electricity, heat and hot water plus mechanical energy if required to pump water.



Residential natural gas prices hit an all time low in December. A survey of some utilities has shown a sell price of $.60 per therm, which equals about $.08 per kwh if you install a Capstone Microturbine. This does not include the 10 percent Federal Tax Credit (for purchase), nor does it include any heat savings which may bring the payback of the microturbine to a very reasonable time.

http://www.globalmicroturbine.com/Site/Microturbine/Microturbine.html

Arcane
05-18-2009, 07:48 PM
Demand meters record the consumption in kwh and show instantaneous demand and also record the peak demand. (Electronic meters show a host of other events also, but that's another story.) After a load is applied the demand starts to register. After one minute, the demand reading is 25% of the actual demand; after 4 ½ minutes, it registers 50% of the actual demand; after 15 minutes, 90%; and after 30 minutes, 99%. Meters read by meter readers get reset at that time, some meters communicate to head office electronically and demand can be taken daily, weekly, bi-weekly or any desired timeframe providing both seller and buyer agreed to it.

J Tiers
05-18-2009, 10:48 PM
Capstone turbines, eh......?

Word has it that they don't sell many, I've seen two scrapped ones (a client is in that business also, and is due to put theirs on the market, if their money holds out). Seen a scrapped Turbec as well. The Turbec is really well built.

The answer on them all is apparently that if you do not need the waste heat, you'll go broke running the turbine just for electricity.



You are saying now exactly what I have been trying to get across but the difference seems to be that you feel this will not hurt anything.

Naw, I been saying the same thing all along.......... I said I didn't know the numbers (nobody but Evan and airsmith do know them) but it might well not be so bad as some early posts put it, and that's still true. Seemed like everyone was saying "you're gonna kill that engine in two hours"..... And we don't know that. Actually, airsmith says he has run it longer than that, and it's still going, so maybe we do have some info..

Might indeed be interesting to see the plug..... among other things.

Evan's experiment was on a different enough setup that it probably isn't a good prediction, but even he said with his setup it wasn't great, but wasn't horrible either.

There is SOME size of chamber and hole that will work OK for sound and backpressure, I don't know, and you don't either, how close to that size airsmith's setup is. We both suspect his is too small, but we can't prove it.

Evan
05-19-2009, 12:48 AM
My setup may look different but in practice it is the same as it is preceeded by the significant volume of the muffler. As I stated, it was my intent to determine if even a relatively mild restriction can cause an increase in temperature. I believe I stated that before I performed the experiment. I was actually surprised by the amount of effect it had on the exhaust gas temperature and that is the most important variable.


We both suspect his is too small, but we can't prove it.


I already have. There is no chance that making the orifice 1.5 times smaller than I used is going to improve the situation.

airsmith282
05-19-2009, 07:57 AM
My setup may look different but in practice it is the same as it is preceeded by the significant volume of the muffler. As I stated, it was my intent to determine if even a relatively mild restriction can cause an increase in temperature. I believe I stated that before I performed the experiment. I was actually surprised by the amount of effect it had on the exhaust gas temperature and that is the most important variable.



I already have. There is no chance that making the orifice 1.5 times smaller than I used is going to improve the situation.

evan you forget there are 2 holes not 1, also you restriced without and exapanstion chamber right at the source so of course its going to have an issue there is not time or cavity for hte exhaust to disapate into before leaving like mine has ,

the larger the cavity the more the air or ehauste pressuer comiming out weakens in this case id bet over 95% has been disapated before ev en getting to the 2 holes i drilled.. given my years of experience with airguns/pellet guns co2 gas pumpers and springers and the designing and builingof muzzle breaks as well, builind this device for my genny was a walk in the park i have also designed and built cutom valves ans pump up system for custom guns so i under stand all to well how air pressures work and affect things .. the closer and smaller the hole you have right at the ehauste part you have less air out put and you choke it right out ,, the amountof air remans the same but you piss it out a a pencel lead you got problems you woof it of a large in the case over 1 inch ID by 7 inch long tube well there aint much left to hit the hole by then ill tell ya, its all but gone pretty much so it can even reverse it self back to the muffler cause it cant reach the muffle hole again when there is even 10% left ..ill take pic of the park plug it was perfectly clean before i added on the device..

Evan
05-19-2009, 08:12 AM
the larger the cavity the more the air or ehauste pressuer comiming out weakens

No it doesn't.

J Tiers
05-19-2009, 09:18 AM
No it doesn't.

Of course it does, Evan..... please open mind and think about it.

With a small expansion chamber the total volume still needs to come out, but it must do it in a short time...... (while the ports are open), because the re is no other place for it to go..... very high backpressure.

With an infinitely large chamber, the gas from one exhaust event still must all eventually leave, but it has one entire rotation to do it...... NOT the short ehaust time. The backpressure will be the average backpressure, with NO pressure spikes.

At any finite size chamber, the peak backpressure DURING THE EXHAUST TIME is higher as the chamber size is made smaller..... if teh chamber is 1/2 the exhaust volume or so, the pressure will be half the exhaust pressure.... neglecting expansion cooling for simplicity.

With a very small chamber, the peak pressure at orifice is identical with the exhaust pressure. With an infinite chamber, the peak pressure is identical with the average.

The higher the peak pressure, the higher the effective average backpressure is...... the spikes drag it up.

Evan
05-19-2009, 10:49 AM
With a small expansion chamber the total volume still needs to come out, but it must do it in a short time...... (while the ports are open), because the re is no other place for it to go..... very high backpressure.


Nonsense. If by some inverted law of physics the pressure became lower the larger the expansion chamber then the LESS the volume of exhaust that would exit the hole because of the lower pressure. That is of course a PARADOX. THE SAME AMOUNT OF EXHAUST MUST LEAVE THE ENGINE PER MINUTE OF OPERATION AT CONSTANT RPM AND OUTPUT REGARDLESS OF THE SIZE OF THE EXPANSION CHAMBER VOLUME.

Would you PLEASE take a look at the photo I posted. This IS NOT an issue of there not being enough volume for the cylinder to empty the exhaust into the muffler. What you are talking about has no bearing or applicability in this case and only serves to seriously confuse the matter.

The engine is 63cc. That is a volume of 4x4x4 centimetres. The muffler plus header pipe is 18 times that size.


The higher the peak pressure, the higher the effective average backpressure is...... the spikes drag it up.


No they don't. The average can't be "dragged up" by pressure impulses since they must be time weighted.

S_J_H
05-19-2009, 12:50 PM
Just add a small nipple to the exhaust muffler and run a length of tubing to a low psi reading pressure gauge. Then test it with and without the add-on muffler.
It would also be easy to make a glass pack style muffler that would reduce noise without adding much back pressure.
Steve

Willy
05-19-2009, 01:46 PM
Just fer yuks I crunched some numbers this morning.

The combined area of both the 9/64's and the 1/8th inch holes is .0278 sq.in.

A 1/4 in. hole has an area of approximately .0491 sq.in., almost twice the area, and considering the lack of boundary layer air flow inherent to any size of port or tube, probably twice as effective in moving air as the 1/8 and 9/64 holes combined. So one 1/4 hole installed at the lower edge of airsmith's muffler mod would move twice the air and also allow it to drain any residual oil that may build up.

The approximately 1/2 exit hole of the muffler has an area of .1963 sq. in., over 7 times the area as the the two holes installed in the muffler extension!

A lot of people make the mistake of thinking that two smaller holes will move a higher volume of air, or any fluid for that matter, than one slightly bigger one. As an other example, a car with a dual exhaust with two 2" exhaust pipes will flow much less cfm of exhaust gas than one with a 3" pipe. Not only does the 3" pipe have a greater cross sectional area than the two 2" pipes, but it is also more effective at moving air because it has less boundary layer frictional loses.

I have also done an approximate calculation of the air requirements of the engine in question in order for us all to have a better understanding of the dynamics involved.

Using an B.S.F.C. (brake specific fuel consumption) figure of .6 (pounds of fuel per brake horsepower hour) the engine would require about 3.5 cfm of air at it's rated output. I have taken the liberty of using a slightly richer air/fuel ratio mixture of 14:1 instead of the stoichiometric correct 14.7:1, a figure that is probably more indicative of real world running conditions. The manufacturer's fuel consumption figures of 4 liters of fuel for five hours at full load are pretty close to what I have, so I am probably in the ballpark at least.

I also have a problem with the incorrect use of the term "expansion chamber" as used in the description of the muffler mod in some posts. In discussing two stroke exhaust systems the term expansion chamber should reflect the true meaning and application of an expansion chamber. Some members have already described the theory and operation of this wonderful tuning aid for two strokes so I won't repeat it here other than to say that an true expansion chamber always precedes the muffler, never after.

A photo showing the dynamics involved in the operation of an expansion chamber:

http://i76.photobucket.com/albums/j31/250willy/ExpansionChamber.gif

Airsmith, if you like I can send you the software used in order to do the calculations involved in determining the dimensions of an expansion chamber to suit any two stroke you decide to build an expansion chamber for.

Another point I'd like to make is that no one here said that this mod was going to turn your genny into a ball of fire within hours. It was pointed out however that it would be detrimental to the longevity of your engine's life.
So look at it this way, you might be satisfied if your engine lives for a 1000 hrs. for example. But I would suspect that without the mod it would probably live for 1300 hrs. Count that as an additional expense incurred in beating Ontario Hydro.
Have you ever wondered that why, in such a competitive market as standby generators, that no one else has successfully done what you have? Many engineers and designers have put in an awful lot of time in balancing engine life, fuel economy, and noise. Learn from someone else's experience, it's what allows us to move forward.


Finally, airsmith the part of this whole discussion that really puzzles me is that although I like your attitude of doing your own experiments to see what works and what doesn't, there are certain fundamentals that one cannot ignore. Many very savvy engine designers from around the world have done an incredible amount of development work on two stroke engines in the last fifty years, it would be ashamed if we ignored their work so that we can make the same mistakes over and over again. A little "book learnin" can not only be fun, it can save a lot of time wasted making the same mistakes that someone else did fifty years ago.

Evan
05-19-2009, 05:50 PM
I happened on an explanation of why the quality is superior to the run of the mill Chinese products. This particular line of generators is made to Yahama's specs as part of a joint venture with Yamaha Japan..



Yamaha Motor has reached a 3-way agreement with the Chinese motorcycle engine maker Jiangsu Linhai Power Machinery Group Corporation (representative: Lu Haimin; Taizhou City, Jiangsu Province, China) and Yamaha Motor's motorcycle manufacturing joint venture Jiangsu Linhai Yamaha Motor Company Limited, known as "LYM" (representative: Lu Haimin; Jiangsu Province), to establish a new company to produce multi-purpose engines. The agreement will be officially signed in Shanghai on August 1, 2003.

The new company, to be named "Yamaha Motor Taizhou O.P.E. Company Limited" (O.P.E. stands for "outdoor power equipment") will be established in Taizhou City, Jiangsu Province in August of 2003 to produce four-stroke multi-purpose engines. The new company will be capitalized at US$3.3 million (approximately 400 million yen), 25% of which will be invested by Yamaha Motor Co., Ltd., 70% by LYM, and the remaining 5% by Jiangsu Linhai Power Machinery Group Corporation. LYM, itself a joint venture between Yamaha Motor Co., Ltd. and Jiangsu Linhai Power Machinery Group Corporation, manufactures and markets complete motorcycles and engines under the Yamaha brand name.

A convenient source of portable power with low noise and fuel consumption. Has a built-in handle for easy carrying. This is an excellent unit for construction sites, camping, or home use. Custom manufactured for XG Power Wholesale Warehouse by Linhai Yamaha so you can rest assured that there will be power when you need it. Includes a 12-volt DC output jack and cables can be used to run equipment or recharge batteries. Six-month Limited Warranty on parts. Generator Specifications: Type: Brushless AVR - Single Phase, AC Frequency: 60 HZ, Maximum AC Output: 950 Watts, Rated AC Output: 800 Watts, Rated / Maximum AC Current: 7.3amps @110 volts, Driving Method: Direct, One 110 volt AC outlet and one 12 volt DC outlet, Dry Weight: 49lbs (22.5kgs), Package size: 16 x 13.5 x 13 inches (41 x 34 x 33 cm), Noise Level: 65 dBa, Engine specifications: Type: 2-Stroke, Air Cooled, Fuel / oil mix: 50:50, Displacement: 63cc, Starting Method: Recoil, Fuel Tank Capacity: 1.1 gal (4 Litres), Recommended Fuel: Unleaded Regular


http://ixian.ca/pics6/genset6.jpg

http://www.portablepowergenerator2.com/yamaha-portable-generator/xg-power-950-watt-electric-portable-electric-power-generator-by-linhai-yamaha.html

http://www.yamaha-motor.co.jp/global/news/2003/08/01/joint.html

airsmith282
05-19-2009, 08:00 PM
hvent check the plug yet do that tomorrow but i tried my 1500 watt ceramic hearer and it ran it great not even a bog down rpms ran up a bit but that was expected never even hit the breaker ..well given that yamaha is in on this genny its no wounder its so good and built right ..

yamaha has always made out standing products

Guido
05-19-2009, 09:05 PM
If I mixed and tried a 50:50 fuel-oil mix, the machine would smoke like a skeeter killer of the first order. Maybe they use different type of lube oil than what we're familiar with?

50 FUEL : 1 LUBE ???????????

G

airsmith282
05-19-2009, 10:11 PM
its supposed to use 50:1 mix only well it runs great on 16:1 to but its suposed to use 50:1

lane
05-19-2009, 10:17 PM
Run her till it blows .Then back off a notch.

J Tiers
05-19-2009, 11:32 PM
Nonsense. If by some inverted law of physics the pressure became lower the larger the expansion chamber then the LESS the volume of exhaust that would exit the hole because of the lower pressure. That is of course a PARADOX. THE SAME AMOUNT OF EXHAUST MUST LEAVE THE ENGINE PER MINUTE OF OPERATION AT CONSTANT RPM AND OUTPUT REGARDLESS OF THE SIZE OF THE EXPANSION CHAMBER VOLUME.




Ridiculous.

It "must" but in one case it likely WON'T....... In the other it has a chance. You may, if you stop with the howling and think about it, see the point.

At the moment you seem to be alone with this perverted physics. There is a world of devices out there, electrical, as well as mechanical, that put the lie to your statements.



No they don't. The average can't be "dragged up" by pressure impulses since they must be time weighted.

You appear to have forgotten that pressure can go to ANY positive value, but is bounded on the lower end by zero..... I will leave it to you to ponder that and see why it makes a difference......... You can be assured that it does, and some thought will show you what that difference is.

Meanwhile, I am now declaring this to be an "Evanment"........ and so I will not be answering any more of your somewhat repetitive objections.

Evan
05-20-2009, 02:04 AM
You appear to have forgotten that pressure can go to ANY positive value, but is bounded on the lower end by zero..... I will leave it to you to ponder that and see why it makes a difference......... You can be assured that it does, and some thought will show you what that difference is.


The difference is one you have not realized. A pressure impulse cannot exist alone but is followed by rarefaction zone. The net effect is that the peak pressure in the wave is cancelled to the extent that the impulse only represents the increase due to the amount of extra matter introduced into a closed volume and not the peak value of pressure regardless of how quickly it may happen or how high it goes. The average pressure cannot exceed the pressure of the same amount of gas in a steady state. That would be a paradox and is contrary to the gas laws.


and so I will not be answering any more of your somewhat repetitive objections.

So stop making repetitive misstatements.

airsmith282
05-20-2009, 08:48 PM
was at walmart tonght they have a 1200 watt with 1000 watt continuoes model exactyl the same in every way , was not a gen mate but some other chines name but every single part is auctually identicaly in every way to the genmate model.. intersting ummmmm

jdunmyer
05-20-2009, 09:20 PM
was at walmart tonght they have a 1200 watt with 1000 watt continuoes model exactyl the same in every way , was not a gen mate but some other chines name but every single part is auctually identicaly in every way to the genmate model..


Well, why don't you buy another one or 2 of 'em so you can run everything from your own gensets instead of the commercial hydro? I think you said you were running your shop lights on your existing genny to save money, so if you can run more stuff from such machines, you'll save even more, right?

I realize that you'll have to build mufflers for the new ones, but your outfit didn't look all that complex or difficult to build.

airsmith282
05-20-2009, 09:38 PM
we gota smarty pants in the circle tonight i like that thats funny..

my plan is to get a 7000 to 9000 watt genny eventualy to run the entire shop off of..

expermenting wiht this little genny is proveing to be interesting, and after all i learned from the honda 300 i rebuilt it has also gieven me ideas and more knolwedge i never had before plus i been doing alot of other research lately as well and will continue ,,i find stuff like this to be very educational at the same time,,,

Arcane
05-20-2009, 10:23 PM
"it has also gieven me ideas and more knolwedge i never had before"


Sorry , but that just struck me as funny as all getout!

gmatov
05-20-2009, 11:12 PM
Arcane,

It is kinda funny. Taught me things I didn't know, would be one way to put it, but airguy says he "don't believe all that **** in the books", to paraphrase.

JTiers seems to have a snit fit with Evan. Evan makes a point, JTiers will take the other side. Even to the point of making nonsensical statements.

You put a 9/64 and 1/8 hole in a 1000 gallon tank and plumb that "genny" into it, the pressure will not rise to the point that you get a little fart out the hole on every power stroke. The fart might lag a bit, as the hole is not at the exhaust.

The exhaust from a 2 cycle has to be well over 100 psi, as the compression pressure is nearly that.

Now, IF the OP had made a larger expansion chamber with a LARGER outlet, he could have reduced the noise.

I am not going back to copy/paste where he says if your "genny" doesn't run faster when you add a load to it, you better fix your "genny". That would work FOR an actual "Genny", a "generator", which produces DC.

An "alternator", an alternating current "generator" MUST run at a given RPM to make usable power. 60 cycle US and a few other areas, 50 cycle most of the world. Number of poles in the machine determine the RPM of the machine.

Airgun guy shoots himself in the foot again when the other guy tells him that he need so much wind speed to get any power from a wind genny. "Yeah, I know they suck." or somesuch. Actually they don't. They will, eventually help with our power needs. All they NEED do is make power at the same cost that the coal, nuclear and water and nat gas plants average out at.

In my part of the US, at least, I think the largest part of my electric bill is other than the cost OF the power. Wires and poles that have not been replaced in 100 years, transformers replaced when the load DOES rise, but still, old plant, and they charge more for transmission over those old, all paid off wires, than the actual cost of the power.

Ah, well, I'm outa this one. Coupla guys that want to piss on each other, I don't gotta listen to that.

Cheers,

George

tdmidget
05-21-2009, 08:11 AM
For what it's worth, Evan is right, among others. It is amusing to see so many try to convince someone who spells and punctuates at less than a second grade level.
My old man always said "Never argue with someone you have to educate first".

jdunmyer
05-21-2009, 08:32 AM
gmatov says:


Airgun guy shoots himself in the foot again when the other guy tells him that he need so much wind speed to get any power from a wind genny. "Yeah, I know they suck." or somesuch. Actually they don't. They will, eventually help with our power needs. All they NEED do is make power at the same cost that the coal, nuclear and water and nat gas plants average out at.


Wind power on a commercial scale isn't all that great, and never will be:

http://www.wind-watch.org/documents/wp-content/uploads/halkema-windenergyfactfiction.pdf

and:

http://www.nerc.com/docs/pc/ivgtf/EON_Netz_Windreport2005_eng.pdf

Nuclear power is the only viable large-scale solution.

J Tiers
05-21-2009, 08:44 AM
JTiers seems to have a snit fit with Evan. Evan makes a point, JTiers will take the other side. Even to the point of making nonsensical statements.


Sir, your statement is the act of an idiot. If you are not an idiot, I suggest that you refrain from appearing as such.

If you find this offensive, I suggest you examine the outrageously offensive nature of your statement.

If you do not understand this post, just ignore it, and continue in your little world.

J Tiers
05-21-2009, 09:19 AM
The difference is one you have not realized. A pressure impulse cannot exist alone but is followed by rarefaction zone. The net effect is that the peak pressure in the wave is cancelled to the extent that the impulse only represents the increase due to the amount of extra matter introduced into a closed volume and not the peak value of pressure regardless of how quickly it may happen or how high it goes. The average pressure cannot exceed the pressure of the same amount of gas in a steady state. That would be a paradox and is contrary to the gas laws.



So stop making repetitive misstatements.

Evan, I have just realized that you are making a different mistake than I imagined..... So I will re-enter this discussion......

Apparently you are objecting to a statement I did not make...... Which explains your somewhat vituperative tone......

You are supposing that I refer to the pressure IN THE SPACE WHICH HAS THE HOLE, and averaging over continuous time.

That is not correct.

The average pressure "dragged up" by the spike pressures is obviously "from the viewpoint" of the cylinder.

It did not occur to me that you would make the mistake of assuming that I referred to the pressure in the large chamber at all times. Obviously the pressure of interest is that which acts to prevent exhaust from leaving the cylinder, and IT is of interest ONLY during the time the cylinder ports are open.

if there is a restriction in the exhaust port, the "average backpressure" will be larger WHEN THE PORT IS "OPEN"....... in other words, the "average" I refer to has NO MEANING at any other time when the port is not open, as it has no influence on the flow of exhaust from the cylinder if there IS no flow..

The gases need to escape the cylinder in a limited time, and with the small opening close by, the pressure must have a very high peak value to allow any significant flow in the limited time.

As soon as the port opens, the pressurized gases rush out the opening into whatever volume exists. if they reach a restriction quickly, and cannot flow farther, the pressure rises quickly.

A small volume, according to the gas laws you reference (P*V = n* R*T), will reach a pressure in accordance with the total volume of cylinder and expansion volume, along with the initial pressure in the cylinder in the instant before the port opens, if you neglect the restricting hole. The effect of the hole is to leak off some of the pressure, and "blunt" the peak of the pressure.

The change in pressure is very large with a small 'closed" volume comparable to the volume of the cylinder.

As a result, the average backpressure SEEN BY THE EXHAUST is large, and it is indeed 'dragged up" by the high spike pressures AS AVERAGED OVER THE "OPEN TIME".

As the volume before the restriction is made larger, the CHANGE in pressure due to the entrance of exhaust into the volume is made less.

Therefore the "average backpressure" seen by the exhaust is lower.

With sufficient volume, the change in pressure is minimal, and the (average) pressure in the volume is AT ALL TIMES, essentially that which is the minimum required to cause one cylinder volume worth of gases to exit through the hole provided over the time of one cycle.

Therefore in that case, the backpressure is the minimum possible value, with NO "spikes" aside from those due to the engine design itself.

With any intermediate volume, the spikes seen by the exhaust will rise above the required average, AND LESS GAS WILL ACTUALLY EXIT THE CYLINDER THAN IN THE CASE WITH A LOWER BACKPRESSURE.

I might point out that the gas laws are of assistance, as the large volume allows more cooling time, and the actual volume of cooled gases will be lower than that of the hot gases "fresh from" the cylinder. That lower flow volume lowers the required average pressure. Since temperature is in "K", it isn't a huge difference, but it is in the right direction.

None of the above is at variance with what I have been saying.........

Evan
05-21-2009, 10:00 AM
You still don't have it right Jerry. Exhaust gas pressures are far higher than the pressure in even a restricted muffler system. The exhaust exits as a pressure wave followed by a rarefaction zone. Cylinder pressures and temperatures go up because the the density in the rarefaction zone is a function of the average pressure in the medium the pressure wave travels in. This particular design has a decent length of header pipe as you can see in the image I posted so that extraction effects will operate well. How well depends on the pressure in the rarefaction zone, not the pressure wave peak.

The peak pressure is dependent on the cylinder pressure and how quickly the port opens (which is a constant in this case). The remaining cylinder pressure is dependent on the amount of extraction that takes place. The amount of extraction is dependent on the average pressure in the muffler, not the peak pressure of the exiting gasses. It's the low pressure zone that allows the gas from the cylinder to exit and determines how much.

The gas that exits the cylinder does not travel at the same velocity as the pressure wave. The pressure wave, like all such waves, is a travelling variation in density of the medium, not an actual continuous movement of that medium at that velocity. The actual gas leaving the cylinder is moving much more slowly into the pressurized environment of the muffler. Regardless of the peak pressure of the pressure wave it is the average pressure that determines how much gas is able to leave the cylinder.

A travelling density wave has no impact on the average pressure since it must be a high density zone followed by a low density zone. It is a sound wave and like a sound wave from a loudspeaker it doesn't cause any net movement of the medium in which it travels.

The only effect that matters is how much gas is injected into the storage space within the muffler compared to how much is able to leave. Since the muffler is not designed to allow the pressure wave to assist in producing extraction effects at the outlet port (which would increase noise) the pressure wave is largely inconsequential.

Circlip
05-21-2009, 10:39 AM
It is a sound wave and like a sound wave from a loudspeaker it doesn't cause any net movement of the medium in which it travels.


Hmmmmmmm good point Evan, you've just dispelled what some very knowledgable sound Ingineers taught me at "Wharfedale", Some sort of crap about the voice coil "Motor" pushing an "As rigid as possible" cone - piston to move air.

Regards Ian

Evan
05-21-2009, 12:08 PM
NET movement. You do know what that means, right? Compare a 500 watt sub woofer to a 10 watt fan. Which one produces a noticeable draft a few feet away?

The loudspeaker is not an air mover. It alternately compresses and rarefies the air creating pressure waves that move through otherwise still air. It is a good simile to what is happening in the muffler when the exhaust port opens. In order for a loudspeaker cone to be an air mover it would have to move in only one direction. I have a few that have attempted that feat.

Willy
05-21-2009, 12:37 PM
we gota smarty pants in the circle tonight i like that thats funny..

my plan is to get a 7000 to 9000 watt genny eventualy to run the entire shop off of..

expermenting wiht this little genny is proveing to be interesting, and after all i learned from the honda 300 i rebuilt it has also gieven me ideas and more knolwedge i never had before plus i been doing alot of other research lately as well and will continue ,,i find stuff like this to be very educational at the same time,,,


You've got to be joking...right?

I don't believe there was one post on this thread that stated you would be money ahead generating your own power, and now you're thinking of buying a bigger unit to do just that!
High efficiency diesel generators with almost triple the fuel efficiency of your present generator aren't even close to being competitive with grid power.

If someone gave you a 7-9 kw. generator and did all of the maintenance, as well as replacing it when it was worn out, (which doesn't take that long under continual usage), you would still be loosing money big time!
Why do you think that no one in the whole world of almost 7 billion souls is doing this and making a profit?

I give up...at least I can admit when I know I can't win.:rolleyes:
Oh well I guess I shouldn't get my panties all bunched up...it's not my money.

Quetico Bob
05-21-2009, 04:09 PM
“Quote
If someone gave you a 7-9 kw. generator and did all of the maintenance, as well as replacing it when it was worn out, (which doesn't take that long under continual usage), you would still be loosing money big time!
Why do you think that no one in the whole world of almost 7 billion souls is doing this and making a profit? Quote”

I would be the first to jump on that offer if it was a little larger unit (400KVA range). I have done the math and know for a fact that we can produce power cheaper based on fuel costs only. Some of us are on demand metering and holy cow does it beat a guy up. When you’re talking almost $4000 delivery on top of your regular KWH usage, it sure would buy a heap of diesel. All it takes is 15 minutes of heavy load out of a 30 day term to incur these rates. No negotiation, no butts, sucks to be you, just so sad and pay the bill or else. So you could count us out as one of those 7 billion souls.

That being said, someone here hit the nail right on the head. About 8 cents will give you 1000 watts of power for 1 hour on the grid in not so many words, doesn’t get anymore matter of fact than that. Math’s a little rusty but based on our gas price that’s about 81ml or near 3 ounces of fuel for our American friends not including the oil.

Maybe our friend is on to something with his invention, all it would take is 3 jiggers of mixed in an empty tank to see how long it would run. If it goes beyond the 1hour mark enough to justify the equipment costs surely an engine can be designed to compensate for the detrimental damage that some here foresee. Might be a better conversation looking for some of those work arounds. The knowledge seems to be here.

Much more of this and I’m going to need a jigger or two myself.:)

Cheers, Bob

Evan
05-21-2009, 05:18 PM
There are about 50 communities in British Columbia that are off the grid where BC Hydroelectric Corp supplies power via very large fixed plant diesel generators. Their average cost to supply that power is about 20 to 25 cents per kilowatt hour but they only charge about 8.5 cents for the first megawatt hour per month. Go over that and you pay full rate plus some. If they can't beat their own cost of generation from hydroelectric then neither can anybody else.

Quetico Bob
05-21-2009, 06:10 PM
Yah, and those rates include union wages. Wish I was getting them.:D

airsmith282
05-21-2009, 08:55 PM
here we also pay for there retiremnt fund which is wronge not upto use to pay there pension fees so they can retire thats upto the employer.. we also pay hi rates for having the power shipped or transfer to us so the bill says in auctual dollars for hte the hydo we use its under 70 bucks then we gewt tageed over 100 and some bucks forhte other fess that are all BS ..so gtetting off the grid is the best thing to do .. and iam sure its cheper in the long run if you use your gennys , inverters and any solor stuff you have combined hooked up properly and used properly you can save a ton of money, start up costs are a bit high but after a few years it all payes for it self,,

i have a customer that uses just invertes off of car batterys and does very well with them and runs his whole house lights tv stereo computer and so on and he aint running no laptop either , genny is used when batterys are recharging from a juker car and solor cells so dont tell me you cant do it or you cant save . mght have to use smaller tools if your a machinest but for hte average joe they wont have the issues some of us would have..

i was looking into a 5000 watt inverter so battery power for it to run , and they bigger genny would not only run my shop at a few hours a day that iam in there but in a power outage runs my whole house when needed .. .

anyhow fight amonge your selfs belive what ever you want to i really dont care ,i still will never belive 100% of what i read only cause i know better,
and i knw for a fact the books are not 100% .. if they were then we all would be better then the computers we program and they mess up all the time so that alone should tell you that all thats in the books is not all 100% thats they way it is and so on and so on and so on..

Evan
05-21-2009, 09:12 PM
When are you going to start using a spell checker? It's almost painful to try and read your postings. If you want people to take you seriously it helps tremendously to communicate clearly.

It won't fix poor grammar of wrong choice of words but it will help you to recognize your own spelling mistakes.

spell checked:

here we also pay for there retirement fund which is wrong not up to use to pay there pension fees so they can retire thats up to the employer.. we also pay hi rates for having the power shipped or transfer to us so the bill says in actual dollars for the hydro we use its under 70 bucks then we get tagged over 100 and some bucks for the other fess that are all BS ..so getting off the grid is the best thing to do .. and I'm sure its cheaper in the long run if you use your gennys , inverters and any solar stuff you have combined hooked up properly and used properly you can save a ton of money, start up costs are a bit high but after a few years it all pays for it self,,


If what you say were true then there would be no power grid, would there?

airsmith282
05-21-2009, 09:50 PM
well you know someday that could very well happen,. but you know the more people that go off the grid or off as much as possible the less money the hydro companies will make and then they will be forced then to drop there rates in order to stay in business.. they over charge way to much , just like the gas companys for our cars for example today we hit a high of 102.9 a liter in good old ontario canada here now only a few months ago was 82 cents a liter.. hello people we are in a recession,, and the barrel of oil is still under 50 bucks , more and more people are riding bikes insteead of fillingup the gas tanks not to save on gas really its cause we cant afford the stuff and wages dont support the increses that change here even 3 times a day utter crap. its hte same gas form 2 hours ago and they jack it up or bring it down its freaking lutercris..

ill never go for an electric lawnmower or electric weed eater thanks i like my gas powered lawn toys. if i ever find my self not affording gas in my car ill ride my bike ,might even put a weed eater motor on it ill get way better miliage then my car does..

i like these new electric powered scooters no liciences no insurance pay your 988.00 and tax and ride it ..now thats some what praticial to a certian degree now if they could only make a built in recharge system so you have unlimited distance then they will be onto something but me fears they dont want to do that yet.. but they sure have the know how to do it ,,

just lke these gen mates 800 watts runing now 1000 watts running noting chaged that i can see and i even pushed it to 1500 watts and still stable, most people read the label and go oh my god i cant do more then this lets count every watt we take up .. so we dont over load it well if you do its gota breaker so you will find its max eventaully so long as the breaker is wokring right.. its there to save the poor thing in the event of an over load.

do i care if i blow it up nope not at all i only paid 20 bucks for it and i fully intend on finding its max limits cause me gota feeling the net model is going to have 1500 running watts, i seen smaller machines capable of 2500 runing watts with the same HP motor and same size power plant so that makes sence to me that this thing might do it to ill certanly let you all know if it frys if so ill have a 2 HP motor to slap on my bike if i blow the unit up.. like i said i dont belive the lables and so far this bugger is taking a beating and no damage thus far and still not kicked the breaker..

I HAVE TO KNOW ITS ALL I CAN SAY I HAVE TO KNOW HOW FAR I CAN TAKE THIS THING..

Evan
05-21-2009, 11:19 PM
The generator (Gen-Mate etc) comes in three sizes, 650, 950 and 1100 peak watts. They are all the same 63cc displacement but they are most likely different in the alternator that generates the power. The engine is rated at 2 hp so that is enough to handle at least 1200 watts output. There probably isn't any difference in the engine part. The difference will be in the wiring gauge in the alternator. They can use lighter gauge wire and save money to produce a lower cost, lower capacity unit such as the 650 watt model. The ratings for peak load are based on being able to handle that load for a certain short amount of time without damaging the wire insulation.

There is a safety factor and the breaker should protect it but if the breaker doesn't trip out then you stand a good chance of burning out the alternator by trying to run a 1500 watt heater. Heaters don't care what kind of power they get. It can be AC, DC 110, 12, 24 or 49.21896 volts and it will still make heat. How much heat will vary depending on the voltage which is what determines the current. Just because the heater is making heat doesn't mean that everything is just fine with the generator. It takes a while to overheat insulation and then a while longer before the windings begin to short out and even longer before smoke begins to drift out.

BTW, I see your spelling has improved. Good job.

gmatov
05-22-2009, 12:05 AM
AND then, too, you got an idjit who tells you what oil is going for.
"and the barrel of oil is still under 50 bucks "

I do believe there was an article in MY Rep paper that says that Goldman-Sachs and the like are the ones who are driving up the price of oil.

They have noplace else to put their money so they try to corner oil.

We have more oil in stock than we have for the last 20 years.]

BEST is that we gave Goldman_Sachs about 85 billion bucks to allow them to screw us even harder.

Oil is over 62 bucks a barrel. ALL of which is rich people making mucho money. MORE oil than we have had in storage for 20 years, and the price is getting to collapse even more of the economy.HERE, I think I have voted for a president that I should not have.

He does not seem to give one damn bit about whether the millions of Americans can maintain their lives.

I am seriously disappointed with my choice of Obama as Pres.


Cheers,

George

Lost a long diatribe TO the Obama web site. Wish I could have saved that and added to it. I am PISSED that I cannot speak to my President without the site shutting me off.

J Tiers
05-22-2009, 12:12 AM
You still don't have it right Jerry. :rolleyes: OK, here we go again..... I'll do it, ONCE....



Exhaust gas pressures are far higher than the pressure in even a restricted muffler system.

Thank you for emphasizing my point!

I might add that they are HOT, and the net volume exiting the cylinder is larger than that taken in... as should be obvious if you consider that heat energy has been released in, but only partly extracted from, the gas.

But please note, I am discussing two extremes, first a very small volume with the hole, as if the port were plugged with just that hole open,. and second a very large volume with the same hole.

All other cases fall between those two.




The exhaust exits as a pressure wave followed by a rarefaction zone.


NOT if the flow is restricted as in the first example...... it is a peak, leaking down to zero..... But probably does not reach zero befoe the port closes again. There is no significant rarefaction, because there is no inertia effect of any consequence with friction removing the kinetic energy of the gas, and the restricted flow that reduces the available kinetic energy to begin with.

Only if the exhaust can flow freely in a pipe of some length is there a significant wave such as you describe. It is an inertial type effect.

The regular open sound wave in free space has a rarefaction, but that is far different from the case here, we don't have a free wave, or free flow in my examples (except large volume).

Besides, there IS mass flow, and so your speaker analogy is "exactly wrong"..... This is a "pump", not a speaker, it MOST DEFINITELY has a net mass flow.

THEREFORE, it ABSOLUTELY CAN have peaks that raise the average pressure, because there is NO REQUIREMENT for the net mass flow to be zero..... QUITE THE OPPOSITE, there MUST be a net mass flow, or the engine will choke and stop..

Your example can only be true for a speaker type action, which this is EMPHATICALLY NOT.




Cylinder pressures and temperatures go up because the the density in the rarefaction zone is a function of the average pressure in the medium the pressure wave travels in.


They go up because some gas does not LEAVE the cylinder, and/or the pre-restriction volume......... more does not leave, the more the restriction. You can keep your "rarefaction zone" (which I suspect you do not fully understand) because in a friction-dominated flow the inertia effects which produce it are not efficient. The system "Q" is low.

This is NOT a free wave in space, it is a pressure AND FLOW within a small pipe we are talking about..... with a lot of friction due to a small hole (and not so much flow in example 1)......



The only effect that matters is how much gas is injected into the storage space within the muffler compared to how much is able to leave. Since the muffler is not designed to allow the pressure wave to assist in producing extraction effects at the outlet port (which would increase noise) the pressure wave is largely inconsequential.

That is, AS I SAID, true for the case of the large volume... in fact I insisted on it. Please re-read. For the actual muffler, we don't know, or at least I don't know, the volumes, but there IS a volume at which the pressure is high, and a larger for which it is lower. A very large volume will have essentially a steady flow out the hole, with some higher-than-atmospheric average pressure and essentially no pressure variation. Cylinder purging will be a function of the purge pressure vs the average backpressure.

It is NOT true for the small volume example, where the cylinder volume is comparable to or larger than, the expansion volume. That will have a large pressure variation above atmospheric, and it may be unable to purge the cylinder properly, because backpressure may be far higher than any purge pressure available. Purging depends on free flow, which is absent with small volume and restriction.

If I simply graphed this for you, I suspect you would see the point.

You seem to think I have zero understanding of basic physics.....which would be a strange state for an engineer who has very successfully done quite a bit of acoustics and electro-mechanical work.

Perhaps if you didn't instantly dismiss what I wrote, but took the time to understand what I said, you might realize that what I am saying is actually based quite solidly on known and accepted physics..... and IC engine principles.

And you are misapplying the behavior of a free-space sound wave to a restricted flow situation.

I will be busy for a few days, which is probably good, this sort of pointless argument takes too much time.

Evan
05-22-2009, 02:16 AM
NOT if the flow is restricted as in the first example...... it is a peak, leaking down to zero..... But probably does not reach zero befoe the port closes again. There is no significant rarefaction, because there is no inertia effect of any consequence with friction removing the kinetic energy of the gas, and the restricted flow that reduces the available kinetic energy to begin with.

Only if the exhaust can flow freely in a pipe of some length is there a significant wave such as you describe. It is an inertial type effect.


Nonsense. A pressure wave travels better the higher the density and the rarefaction zone matches it. Friction isn't a factor since the pressure wave doesn't directly involve a flow. Sound waves can travel under water across the entire Pacific Ocean. The worst condition for the transmission of a pressure impulse is "if the exhaust can flow freely in a pipe of some length ". That's why a proper expansion chamber has a relatively small outlet. You can't propagate a pressure pulse in a vacuum and the lower the pressure the poorer the propagation.


THEREFORE, it ABSOLUTELY CAN have peaks that raise the average pressure, because there is NO REQUIREMENT for the net mass flow to be zero..... QUITE THE OPPOSITE, there MUST be a net mass flow, or the engine will choke and stop..



Completely incorrect and impossible. Pressure peaks are followed by pressure dips. The pressure of a changing quantity of gas in a fixed volume is in no way dependent on the rate of change ( disregarding heat losses), only on how much it changes and the temperature of the gas.

You are also missing entirely the fact that the temperature base point for ideal gas law calulations is absolute zero. There is plenty of room for equal and opposite rarefaction zones to exist.

You are talking through your hat Jerry.

David Powell
05-22-2009, 07:36 AM
I have followed this correspondence with interest. My experience as a machinist working for a lifetime of various employers and especially in experimental and educational establishments has taught me that if someone can explain a theory in simple enough terms that I can grasp the basic outline of that theory their experiments or equipment are likely to be successful. Conversely, if they present their theory in a way in which does not make it clear to me, then, no matter how hard everyone tries, the experiment or equipment is very unlikely to be successful. My countryman " Up North" is , from the sound of his postings( Havent yet met him, hope to some day) a very enthuiastic" Home shop machinist" and as such deserves as much help as possible. Continual banter about complex theory does not help much, explaining that theory in an understandable fashion would. I learned a lot of basics from a well educated steam roller driver who explained the theories by drawing in chalk on the rolls of the steam roller while we waited for the next load of stone. Please can we become tolerant and kind towards those who havent been so fortunate and who perhaps need simpler explanations. Regards David Powell.

rotate
05-22-2009, 08:37 AM
David, I'm also a fan of making theories simpler to understand, however there are many concepts which cannot be dumbed down. For example, it's almost impossible to explain how fourier analysis works (which is necessary to explain how mp3 compression works) without having studied math beyond highschool. Even then, it can be difficult to understand.

One of the follies of over simplifying a scientific concept is that it can lead to false conclusions because the simplified model does not account for the boundary conditions and the influence of hidden variables. Just because two variables exhibit linear relationship over a broad range, it does not mean that you can extend that to the extreme.

airsmith282
05-22-2009, 08:56 AM
I have followed this correspondence with interest. My experience as a machinist working for a lifetime of various employers and especially in experimental and educational establishments has taught me that if someone can explain a theory in simple enough terms that I can grasp the basic outline of that theory their experiments or equipment are likely to be successful. Conversely, if they present their theory in a way in which does not make it clear to me, then, no matter how hard everyone tries, the experiment or equipment is very unlikely to be successful. My countryman " Up North" is , from the sound of his postings( Havent yet met him, hope to some day) a very enthuiastic" Home shop machinist" and as such deserves as much help as possible. Continual banter about complex theory does not help much, explaining that theory in an understandable fashion would. I learned a lot of basics from a well educated steam roller driver who explained the theories by drawing in chalk on the rolls of the steam roller while we waited for the next load of stone. Please can we become tolerant and kind towards those who havent been so fortunate and who perhaps need simpler explanations. Regards David Powell.

hi david any time your in north bay come by for a vist iam usualy here i work at home. i love my job,,
im of the generation of keep it simple and i under stand makeit complex forget it i cant comprehend,, if someone wants something built i build it so long as my machines and me can do it i just do it.
if i can then i can pretty simple to me there..
yes i know how to use calipers and micrometers and stuff like that..

i work on small engine and cars when i have to i hate cars these days anyhow i so ther stuff to i dont limit my self to what i do with machines and so on,..
i do under stand air pressures all to well due to years of messing with pellet guns, so you can apply some of the knolwedge in small engine stuff to anyhow thats another subject all togeter..

well ok for the voting guy there, you can never vote for the wronge guy, so i have been told,, cause if you dont vote at all then your vote goes to the guy thats in the lead anyhow..

to me i dont vote any more,whats the point there both the wronge guys. we all get screwed and it dont feel good.. this thing on if you vote you got rights you got nothing no rights at all its another false statement more lies out of their mouth ,, been there done that

im not into politics my self i think its all bull crap and lies just so some one else can make a crap load of cash for a few years and screw us more and so on..

now for the wattage on the genys here , Evan how much room do you think is inside thoes gennys to support larger wire gauges.. you gota lot to learn there my firend , i know your not my firend its a fiqure of speech.. any how i use a standard size 100 foot extenson coard that has my lights my lathe and a buch of other crap on the line drawing same time this was before the genny and it has a computer power coard on it to plug it inthe wall origianl plug got nailed so i wired me on a cheap fix now for 4 years its been like this wand no over heats or melt downs and its only a rated 10 amp cord my lath wants 15 amp just to fire up ,so you going to tell me iam going to start a fire or a melt down i never even tripped the breaker yet either in 4 years.. now my old old 90 amp cracker box wants 30 amps ,has 10 amp 120 volt cord on it and i can weld for 5 min before i trip the breaker in the house which is acceptable even a larger gauage wire is not going to stop that from happening ,,

sorry evan but i was designing stuff in electronics sence i was 9 years old iam now 40 years old , dont tell me it cant be done. i understand stuff on a different level then most others, iam the kinda guy if i can do it i will if what iam doing or want to do can be done ill find a way..

anyhow i gota go guys i gota get weed eater and lawmower done before 12pm

J Tiers
05-22-2009, 09:12 AM
Nonsense. A pressure wave travels better the higher the density and the rarefaction zone matches it. Friction isn't a factor since the pressure wave doesn't directly involve a flow. Sound waves can travel under water across the entire Pacific Ocean. The worst condition for the transmission of a pressure impulse is "if the exhaust can flow freely in a pipe of some length ". That's why a proper expansion chamber has a relatively small outlet. You can't propagate a pressure pulse in a vacuum and the lower the pressure the poorer the propagation.


Evan, you are so far out in left field that you have left the parking lot, let alone the field.........

have you lost sight of the fact that the engine IS A PUMP? THERE IS FLOW OF GASES

Your theories about sound waves are all very well, IF THAT WERE THE ISSUE, BUT IT IS NOT.



Completely incorrect and impossible. Pressure peaks are followed by pressure dips. The pressure of a changing quantity of gas in a fixed volume is in no way dependent on the rate of change ( disregarding heat losses), only on how much it changes and the temperature of the gas.

When the pressure peaks are due to FLOW, there is no requirement for an equal and opposite rarefaction. There can't be one, or there would be no net flow. Flow can exist just fine with a check valve, which prevents reverse flow.

A free sound wave is NOT a flow situation, and the medium theoretically returns to its initial state/ position after the wave passes.

Air and fuel enter the engine in one place, and EXIT from another. it is obvious on the face of it that there is net flow THROUGH the engine, IN ONE DIRECTION.

This is not "over unity physics", it is first semester stuff.

Restrictions to that flow restrict MORE severely when they are 1) in an area requiring high flow in a limited time, and less so when they are in 2) an area which requires only a lower flow for a longer time.

if you take a given orifice, and require a particular gas volume to flow through it, but restrict the TIME to a short period, it is obvious that the required [pressure will be high.

if you allow a longer time, the pressure required will be lower.

The ports are open a short time only....... the flow of a certain volume is required, and a given orifice may not allow that flow without a very high back pressure. That back pressure exists only while the ports are open, but that is the IMPORTANT time..

The same orifice, if allowed a longer time for the same volume to flow, will not need as high a pressure.

Therefore the restriction close to the port will cause a larger PEAK PRESSURE, (restricts flow more), than the same restriction along with a large volume which has the port open time PLUS the rest of the cycle time for the same volume of gas to flow out.

You can look at that from any viewpoint you want, and it is still true.

Case 1 is near the port, with minimal expansion volume, case 2 is after a large expansion volume.

It is incredible that you are not seeing this. You are smarter than that.



You are also missing entirely the fact that the temperature base point for ideal gas law calulations is absolute zero. There is plenty of room for equal and opposite rarefaction zones to exist.

You are talking through your hat Jerry.

Evan...... your statements have reached the ridiculous.....

1) I SPECIFICALLY mentioned that the temp range was not what it looked since it is in deg K...... Your statement is ABSOLUTE PROOF that you have NOT read what I wrote, and are just reacting to your own distorted idea of what I wrote.

2) Saying that someone is 'talking through their hat" is not equal to proof. It is merely somewhat "ad hominem abusive".

3) You are misapplying free wave acoustics to a pumped flow situation, and you either do not realize, or refuse to realize, that fact. This is not worthy of your generally high intelligence. (while acoustics generally do apply, it is important to realize what does NOT apply).

I am forced to the conclusion that you have no intention of discussing the problem. Apparently you have already made up your mind that you are never wrong, cannot be wrong, and therefore even the soundest argument against your statements is obviously wrong... And that if you just insist and persist, your 'adversary" will give up and thus "prove you are right."

Well, if you want to be right that much, you can be "right", at least in your own mind. It won't change reality, of course.

I am sure that Radkins understands what I said, even if he doesn't think the engine will run well with those dimensions, a point I am willing to agree depends on the details.

Evan
05-22-2009, 09:23 AM
The problem is your continued insistence that pressure peaks will somehow "raise the average" pressure. The only way to interpret that is that the pressure would be lower if the peaks did not exist but the total flow is the same. It matters not one bit what the peaks are and you continue to either fail to understand that or are intentionally ignoring that. You are also failing to understand or acknowledge the difference between an acoustic impulse, which by the way is what is responsible for the noise a running engine makes, and the actual flow of gases, which is not responsible for the noise. If it were, then a muffler would be ineffective.

You also made the statement that the temperature is bounded on the lower end as if that actually means something. Since when has the exhaust of an IC engine ever approached absolute zero? It is a limit without consequence.

You have dug yourself into a logical hole and there is no way out of it.

lazlo
05-22-2009, 10:44 AM
I have done the math and know for a fact that we can produce power cheaper based on fuel costs only.

The current price of oil and gas is temporarily depressed because we're 18 months into the worst recession in 26 years. Once the world's economies start to recover (the economist consensus seems to be Q1, 2010), oil (and gas) prices will shoot right back up to 2006/2007 prices.

Evan
05-22-2009, 12:27 PM
I am counting on it.

Quetico Bob
05-22-2009, 01:41 PM
:eek:
Well arn't you two just a bundle of good news and joy. I was just getting used to being able to budget more than one trip a week to town. How long can fuel be stabilized for?

Cheers, Bob

Evan
05-22-2009, 03:07 PM
The oil and gas market is my favourite investment. It's very easy to predict. When everything tanked it became the biggest buying opportunity in a very long time. No matter what happens the appetite for fossil fuels isn't going to disappear.

J Tiers
05-22-2009, 07:21 PM
The problem is your continued insistence that pressure peaks will somehow "raise the average" pressure. The only way to interpret that is that the pressure would be lower if the peaks did not exist but the total flow is the same. It matters not one bit what the peaks are and you continue to either fail to understand that or are intentionally ignoring that. You are also failing to understand or acknowledge the difference between an acoustic impulse, which by the way is what is responsible for the noise a running engine makes, and the actual flow of gases, which is not responsible for the noise. If it were, then a muffler would be ineffective.

You also made the statement that the temperature is bounded on the lower end as if that actually means something. Since when has the exhaust of an IC engine ever approached absolute zero? It is a limit without consequence.

You have dug yourself into a logical hole and there is no way out of it.

Whatever you say in your personal perverted version of logic and physics.

Most of what you have said above about my statements is false. You presumably have the brains to understand why and how this is the case.

May I suggest you USE them.

John Stevenson
05-22-2009, 07:53 PM
hi david any time your in north bay come by for a vist iam usualy here i work at home. i love my job,,
im of the generation of keep it simple and i under stand makeit complex forget it i cant comprehend,,

That simple you are using 4 letters when the word has 7.

It makes me wonder what part is simple ?

.

airsmith282
05-22-2009, 09:44 PM
well we hit 112.9 a liter today,,,

John Stevenson
05-23-2009, 04:48 AM
well we hit 112.9 a liter today,,,

Is that cat litter or a Queen Ann litter ?

.

Norman Atkinson
05-23-2009, 08:35 AM
John,
Queen Anne had legs so she she didn't need a litter.

Obviously, he is referring to liters for fags. They get the ends hot.


Norm

airsmith282
05-23-2009, 09:26 AM
1.12 .9 aka 1 dollar and 12 cents a liter ,,sorry we dont use the gallon SAE system in canada

and yes i hate the metric system is sucks .

either way its sucks gas prices are due to sky rocket were in a recession now its going to cost me 60.00 instead of 40.00 thats 3/4 of and hour of work to fill up my gas tank in my car,, oh well guess ill have to ride my bike more..
it would be so nice if the govenment could stick there nose where is does belong and put a cap on gas prices and set it at even 70 cents a liter might just help the econmany a bit at the same time..

not likey to happen but nice to dream about ,, even my lathe and my mill got jacked up in price a few houndred dollars each not that iam not going to complain about to much,,

ok now for todays laugh,, the stanely black chrome socket set at canadain tire is selling for 299.00 right now regual price it goes on sale for 119.99 or 99.99 i bought mine when it was on sale for 119.99 and how some kid to me he was a kid probley 20 years old any how grabs a set without looking the all chrom set is on sale right now ,, thanks i live my black set any how not 20 min later he puts it back guess he gota surprise at the check out lol .. 2 weeks ago some guy auctually paid 299.99 for it,, now iam sorry but the tools event eh master craft ones are not worht that kinda money when they can afford t sell them for 60 and 70% off regular price..

last nite my son bought his first socket set 166 peice mastercraft for 69.99 regular price was 179.99 so thats a 60 % savings good deal.. never buy until its on sale its always worth the waite..

John Stevenson
05-23-2009, 02:13 PM
1.12 .9 aka 1 dollar and 12 cents a liter ,,sorry we dont use the gallon SAE system in canada


Obviously don't use the metric system either....




.

Norman Atkinson
05-23-2009, 03:49 PM
[QUOTE=John Stevenson]Obviously don't use the metric system either....


And as all things are written in French and English- the mind boggles

Eh Bien, Mon Vieux

Le Norm

David Powell
05-23-2009, 05:05 PM
We have got nearly every measuring standard in the whole world in current use here. Our population has come from all over the world, especially in the last few years. Some folks naturally measure in Imperial. some in Metric and some in 'other' ways. Our equipment and machinery is largely imported, again from all over the world. Frequently, we find need to " marry" metric parts to Imperial. Many of the drawings I have worked to have been a mix, eg tap 12 4/40 threads on a 40 mm pcd. My big milling machine, a Pedersen made in Denmark in the 60s has all Whitworth threads, My little chinese mill has1/4" 20 bolts with 10 mm heads. Its no wonder we are a confused country, our politicians arent even bright enough to be successful crooks. We have two real seasons, winter and road construction. In neither of them can you be sure of getting anywhere without lots of exciting delays and diversions. Don't blame us for anything, it all just seems to happen. Where else calls electricity " HYDRO"( We still use water diverted fro Niagara falls to generate a lot of ours)??? Regards David Powell.

Quetico Bob
05-23-2009, 07:07 PM
Nice score on the socket set, like their stuff when its on sale can't beat the price or the life-time warranty. My Son has his own 1/2 socket set too!
1/2 of mine are at the shop the other half are on his Bob the builder work bench at home.....umm, his?

Here's a neat little work around, not sure why it just popped into my head, but in a pinch. Did you folks know that a battery out of a Luner Jim communicator wrist watch is the exact replacement for a Mitutoyo .0001 digital mic. Saved me a special trip to town and a litre or two of gas!

Cheers, Bob

lazlo
06-08-2009, 09:41 AM
the barrel of oil is still under 50 bucks , more and more people are riding bikes insteead of fillingup the gas tanks not to save on gas really its cause we cant afford the stuff and wages dont support the increses that change here even 3 times a day utter crap. its hte same gas form 2 hours ago and they jack it up or bring it down its freaking lutercris..

I HAVE TO KNOW ITS ALL I CAN SAY I HAVE TO KNOW HOW FAR I CAN TAKE THIS THING..

So now that oil is nearly $70/barrel (and rising), have you recalculated your costs?

airsmith282
06-09-2009, 08:06 AM
nope never re calculated my costs ,, i dont much care a about it over all, what the oil costs are,, i already know the planet is going to hell in a hand basket ,, the price of 2 stroke oil seems to have stayed the same, i do how ever have a bitch here about that stuff, the synthic stuff is like 3 times the price and almost 3 times less in amount in the bottle then the real stuff , why the hell is that if the fake stuff is supposed to be better for the OZONE and so on and do better how come its 3 times the buckers of the real oil , regual motor oil vs fake stuf is same deal fake is tripple the price, its not goingto last any longer and surley can not be any better for the engine any how i see no benifits of using fake oils and costing 3 times more money as well thats crooked..

if they want to solve a great deal of polution then get rid of the big problem which is diesel cars and trucks and motors that use the stuff,
turns out our wonderfull city is now going to pass a by law that you can no longer idel your cars with in 100 meters of a school and the busses will also have to shut down as well , thats going to be a bitch in the winter for the diesel engins the hate starting when it gets bitter cold.. they are also talking about a city wide ban cars and trucks and bus's idleing the engines..

welcome to hell i say, where do they get off on these ideas there are worse things then car exhaust and ciggerettes ,,

oh well sorry for the rant having a bad week sence we got the news on the new by law,,

you know we got over 22,000 different by-laws in this city its nuts
pretty soon we wont be able to take piss without permision, watch them out law sex to someday,wont that be cool NOT...

oh well i seen this crap comming just didnt think in my time it would happen but guess i was wronge :( :( :(

digger_doug
06-09-2009, 09:54 AM
Where else calls electricity " HYDRO"( We still use water diverted fro Niagara falls to generate a lot of ours)??? Regards David Powell.

Dave,
I was preparing some installation prints for a machine that came
from your area. By watching canadian T.V. I know the term
"hydro" means electricity. Now this company used that term for the
electrical hook up (where I needed to set a conduit), but there
was a water hookup as well for a spotwelder cooling circuit
(on the other side of the machine I might add).

I had them "redefine" their designation on the print....